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Review article
Supported by a grant from Zeneca Pharmaceuticals

Pollen identification
Richard W Weber, MD*

Learning Objectives: The purpose of this review is to introduce the reader to a
systematic approach to categorizing pollen types. This will enable the reader to
recognize pollen characteristics of the most common botanical sources and determine the relevant contributors to the local aeroallergen burden.
Data Sources: Allergenic plant and pollen atlases for pollen characteristics,
allergy texts for procedures and overviews, and relevant reviews from the English
medical literature (1985 to present).
Results: By applying a visual gestalt utilizing grain number, size, shape, surface
structures, and internal detail, one is able to identify pollen source to the appropriate
botanical taxonomic level. Identification may be possible only to the family or
order, but most frequently to the genus, and occasionally to the species.
Conclusions: Outdoor sampling allows the identification of aeroallergen burden
in a locale. In conjunction with field work, the relevant sources can be identified as
well as time of pollination. This allows the physician to correlate symptoms with
exposure and relevant sensitization.
Ann Allergy Asthma Immunol 1998;80:141–7.

INTRODUCTION
The purpose of this review is to provide a basis for identification of the
majority of aeroallergenic pollens.
Through the consideration of several
variables discussed below, the observer can develop a system of pattern
recognition, or gestalt, to assist in characterizing the airborne burden in a specific locale. This should be combined
with a familiarity with what plants are
actually growing in the area of concern. This may be best achieved by
contacting a botanist who has knowledge of the local flora. Such a person
may be working for a community or
state government, or perhaps a university extension. Additionally, there are a
number of texts that catalogue regional
plants, and the interested party will
* From Department of Medicine, Allergy/
Clinical Immunology Division, National
Jewish Medical and Research Center, Denver,
Colorado.
Received for publication August 11, 1997.
Accepted for publication in revised form
December 9, 1997.

VOLUME 80, FEBRUARY, 1998

find these helpful resources.1–3 Field
trips at varying times of the year will
familiarize one with the times of anthesis for the local plants. Knowing the
local flora will assist in identification
of the particles found on the sampler;
this in turn will allow interpretation of
patient’s symptom chronology and the
relevance of in vivo or in vitro sensitivity.
This review will use numerous descriptive phrases that are not common
usage. These terms are defined
throughout the text. For ease of referral, these phrases are placed in bold
face where they are defined.
BACKGROUND
Higher plants use two methods of pollen dispersal: wind or vector. While a
variety of animals may transport pollen, insect vectors are by far the most
prevalent. Plant pollinated through the
agency of an insect carrier are called
entomophilous. Only about ten percent of higher plants utilize wind pollination, these are called anemophilous, and are the principle cause of

pollinosis. Plants that typically are
both insect-pollinated and wind-pollinated are amphiphilous. Some primarily entomophilous plants, such as
linden (Tilia), produce a large enough
pollen load that appreciable surplus
amounts become airborne.
SAMPLE PREPARATION
Principles of aeroallergen sampling
have been reviewed previously by
Burge.4 The reader is referred to that
article for discussion of techniques and
tabulation. Advantages of various samplers will not be discussed here other
than to state than older gravimetric
techniques such as the Durham sampler are no longer adequate, and volumetric sampling is strongly recommended.
Once the sample is obtained, it is
necessary to prepare it for microscopic
examination. Pollens may be stained
with numerous agents, but the standard
preparation is with Caberla’s solution,
which utilizes basic fuchsin. This stain
permanently stains the pollen outer
wall (exine), while not staining the
great majority of mold spores; it imparts a pink to red color to the pollen
grains, which persists in permanent
mounts. The formulation of Caberla’s
solution is as follows5:
glycerin
5.0cc
95% ethyl alcohol
10.0cc
distilled water
15.0cc
saturated basic fuchsin
2 drops (or ⬃50mg powder)
If the solution is staining too intensely, it may be diluted with the dyefree solution.

141

MORPHOLOGY IN POLLEN
GRAIN IDENTIFICATION

Figure 1. Composite cross-sectional detail of pollen grain wall (not all features found on individual
grains). Surface projections not drawn to scale for ease of illustration. See text for definitions.

STRUCTURE OF POLLEN
GRAINS
The pollen wall consists of three layers, the outer two comprising together
the exine, and the inner layer the intine. The exine is resistant to degradation, and withstands acid-heat exposure (a process called acetolysis). The
intine is cellulose, and is susceptible to
such treatment. Beneath the intine lies
the cytoplasm of the grain, or the protoplast, enveloped by the cell membrane, the plasmalemma (Fig 1).1 The
exine has two layers: the innermost
featureless, but impervious, nexine,
and the outer sexine, which is penetrated by numerous micropores, as
well as larger apertures: pores and fur-

rows. These apertures are areas of
thinned exine, and act as points of
egress for the pollen tube during successful pollination. The apertures and
micropores probably also act as avenues for the elution of allergenic proteins, which may have enzymatic and
signal recognition functions in instigating the fertilization process. The sexine may have separate sublayers: an
outer roof, or tectum, a foot layer
abutting on the nexine, and a central
segment comprised of columns, or
baculae, separating the two. Additionally, the outer surface of the sexine
may have a variety of projections and
surface markings which are discussed
below.

Figure 2. Photomicrographs showing representative shapes and clusters of pollen grains (not all same
scale). A. spherical monoporate monad (grass, Graminae); B. wedge shape (bulrush, Scirpus); C.
rhomboid tetrad (broadleaf cattail, Typha latifolia); D. split exine and extruded intine and stellate
protoplast (cedar, Juniperus); E. square shape (ash, Fraxinus); and F. grain with two air bladders (pine,
Pinus).

142

Number of Grains
The majority of pollens captured on
samplers are single grains, or monads.
Representative pollen types are shown
in Figures 2 and 3. Some, however, are
multiple, such as the 16-grain mimosa
(Acacia) polyad, or the 4-grain tetrad
of broadleaf cattail, Typha latifolia
(Fig 2C). The latter is a “rhomboid”
tetrad, while wood rush, Luzula, and
members of the heath family (Erica)
have a tetrahedral configuration. Occasionally, pollens will clump together,
giving the appearance of a polyad, but
with a little pressure on the coverslip,
these will usually separate easily.
Size
Pollen grains vary greatly in size, from
2 to 5␮m to about 250␮m, although
most wind-pollinated grains are between 20 to 60␮m. Nettle, Urtica, and
the mulberries, Morus and Broussonetia, all produce pollens in the 10 to
15␮m range. While corn, Zea, and
some conifers, Abies and Pseudotsuga,
may be over 100␮m. Certain entomophilous pollens such as pumpkin,
Cucurbita, may be as large as 250␮m.
Shape
Pollen grains are generally elliptical or
spherical, but other distinct shapes exist. Pine, fir, and spruce pollens (Pinus,
Abies, and Picea, respectively) have
two air bladders, or vesicles, one either
side of the grain. This gives the pollen
grain a “Mickey Mouse cap” appearance when viewed in the equatorial
plane (Fig 2F). These bladders may be
either clear, taking on the fuchsin stain,
or be darkly pigmented. Footballshaped or triangular are not uncommon, or even wedge-shaped, like a kernel of corn (sedge and bulrush, Carex
and Scirpus, Fig 2B). Pores in the grain
may act as points on the surface where
the exine angles, giving the pollen a
triangular, square, or polygonal shape,
depending on the numbers of pores
(ash, Fraxinus, Fig 2E). An exception
is linden, which has three pores occupying the flat sides of a somewhat triangular shaped grain, rather than the

ANNALS OF ALLERGY, ASTHMA, & IMMUNOLOGY

Figure 3. Photomicrographs showing representative pollen grain surface features (not all same scale).
A. three-furrowed, tricolpate (maple, Acer); B. spined, echinate, tricolporate (sunflower, Helianthus); C.
periporate chenopod-amaranth; and D. triporate grain with distinctive aperture features of annulus, aspis,
and oncus (birch, Betula).

corners. In the case of sages (Artemisia), the exine invaginates somewhat
at the pores, bulging between, giving
the grain a distinctive scalloped
appearance.
The degree of elongation of elliptical pollen grains can be used in identification. Kapp suggested using the
ratio of polar to equatorial diameters,
the P/E index.6 The pole of a grain
is defined as either the location of a
single pore or midpoint of a single
furrow, or the end where furrows
converge (tricolpate or tricolporate
grains). The following descriptive
phrases are used depending on the P/E
index:
⬎2.0
perprolate (very elongated)
1.3–2.0
prolate (slightly elongated)
0.75–1.3
subspheroidal
0.50 – 0.75
oblate (slightly flattened)
⬍0.5
peroblate (very flattened)
Surface Structures
The majority of pollen grains can be
identified by surface structures in the

VOLUME 80, FEBRUARY, 1998

sexine, the most distinctive being apertures: pores and furrows (Fig 4). Additionally, projections off the grain
surface may be characteristic, as may
be ridge patterns on the pollen surface.
These structures are the primary means
of identification to the taxonomic level
of genus, and can sometimes delineate
species.
Pores. Pollens with pores are called
porate. Pores are primarily circular,
but sometimes elliptical, and may be
single or multiple. The appropriate
prefix specifies whether there is a single pore, two, three, or numerous pores
(mono-, di-, tri-, or periporate, respectively). Members of the grass family
invariably are monoporate, as are several grass allies (Fig 2A). Triporate
grains are perhaps the next most common. A few species have two pores,
such as the mulberries and wood nettle
(Parietaria), and occasionally aberrant
grains of species normally having 3
pores (nettle and birch, Urtica and Betula) will only possess two. Weeds of
the closely related chenopod and amaranth families have multiple pores,
generally between 20 and 80 per grain.
Under the microscope, these pollens

look like golf balls (Fig 3C). In distinction, plantains (Plantago) have
fewer pores, usually 6 to 11. Sweet
gum, Liquidambar, has 12 to 20 pores,
which are bulging with dark granules.
Grains with ⱖ4 pores oriented along
the grain’s equator (crown-like) are
called stephanoporate (Fig 3). For
some periporate pollens such as walnut, Juglans, the pores are entirely on
the equator and one hemisphere.
There are several modifications of
the exine around pores which may be
helpful in classification (Fig 5). The
pore sometimes possesses a cap or
plug, the operculum. An aspis is a
thickening of the exine around a pore,
like a shield. An annulus, or ring,
around the pore may either be a thickening, or a thinning of the exine. A
thickening of the intine under a pore is
called an oncus. A band may arch between pores, and is called an arcus;
although it may appear to be within the
inner portion of the grain, it is thickened sexine, forming a ridge along the
surface of the grain. Birch is a triporate

Figure 4. Types of pollen apertures (structures depicted in dotted lines are situated on far
side of pollen grain). A. inaperturate; B. monocolpate; C. tricolpate, equatorial plane; D. tricolpate, polar view; E. tricolporate; F. periporate;
G. monporate; H. triporate, equatorial plane; I.
triporate, polar view; and J. stephanoporate.

143

pollen with a very distinctive annulus,
aspis, and oncus (Fig 3D). Alder, Alnus, which is pentaporate, likewise has
distinctive aspides and very prominent
arci. While some species of birch may
have arci, these are much less apparent
than with alder grains.7,8
Furrows (colpi). These are slits or
boat-shaped areas of thin exine (Fig 4).
Grains with furrows are called colpate.
The furrows may be quite long,
stretching from pole to pole, or be
quite short and unapparent. The same
prefixes are used as with pores to designate number and orientation. Pollens
which possess both furrows and pores
are called colporate. The pores in such
cases are located within the furrows,
which occasionally may be quite short,
barely extending beyond the pore, as
seen with the ragweeds, Ambrosia spp.
Maples and oaks (Acer and Quercus)
are colpate but may show bulging furrows which appear colporate in polar
view (Fig 3A).
Sculpturing. Surface texturing into
ridges or depressions may occasionally
identify one species from another, although such detail is frequently difficult to discern under normal conditions
of light microscopy. A pollen with a
smooth surface, such as with the
grasses, is called psilate. Patterns may
be reticulate (net-like), striate (roughly parallel ridges), or rugulate (irregular pattern). Most maples have a
distinctly striated surface; boxelder,
however, has a more irregular pattern.
Cottonwoods, Populus, have a granular, irregular surface texture.
The roof of the exine may have
prominent projections of various
shapes: baculate, or rod-like; clavate,
club-like or tennis-racket shaped; echinate, spiny; gemmate, door knob
shaped; scabrate, rough or flecked;
and verrucate, warty or bumpy (Fig
1).6 These projections may be very distinctive, and readily apparent, or may
be very subtle and hard to see, requiring careful observation under high resolution with oil immersion. Many
composite weeds (including the ragweeds, Ambrosia) have obvious spines
(Fig 3B). Those of the ragweeds are
short and broad-based, while those of

144

Figure 5. Composite cross-sectional detail of pore-associated structures (not all features found on
individual grains). See text for definitions.

primarily entomophilous species such
as goldenrod and sunflower (Solidago
and Helianthus, respectively) have
longer spines. Sages are baculate, but
the rod-like projections are less easy to
appreciate. Bald cypress (Taxodium)
and redwood (Sequoia) pollens resemble those of the cedars and junipers
(see below) with the exception of a
single irregular projection, an “exit papilla.”
Interior Structures
While the protoplast of many pollens is
nondescript, internal characteristics of
certain pollens are helpful for identification. The presence of a thick intine
helps identify cottonwoods. The intine
may be particularly dense, as seen with
Cypress family members (cedars and
junipers, Juniperus), with an irregular
stellate appearance of the protoplast.
Juniperus species, particularly, have a
thin exine, which frequently splits
open on the microscope slide, extruding the clear round intine and protoplast portion of the grain, leaving the
stained exine appearing like a “Pacman” (Fig 2D). Docks and sorrels,
Rumex, have prominent internal starch
granules, giving the interior a “popcorn” appearance. Grasses also have
starch granules, but these are much
less apparent.
SUMMARY OF MAJOR
AIRBORNE POLLEN GROUP
CHARACTERISTICS
The following section summarizes pollen attributes of the major groupings of

aeroallergenic plants. It is not meant to
be exhaustive, but rather highlights the
average appearance and significant
characteristics within each group. Pollen characteristics have been derived
from several sources.6 –12 Further botanical taxonomic information on these
plants may be found in several sources.1,13,14
Pinaceae
Members of the pine family (pine,
spruce, and fir; Pinus, Picea, and
Abies, respectively) generally have
two air bladders, are inaperturate, and
range in size from 40 to 100␮m.
Larches and Douglas fir (Larix and
Pseudotsuga) do not have vesicles.
Hemlocks (Tsuga spp.) may have two
bladders, which are either fully formed
or rudimentary, or have none.
Cupressaceae
Cedars, junipers, and arbor vitae (Juniperus and Thuja spp.) are psilate and
inaperturate, and smaller than pines,
ranging from 20 to 35␮m. A markedly
thickened intine is up to 6.5␮m.
Taxodiaceae
Bald cypress and redwoods (Taxodium
and Sequoia spp.) are up to 36␮m,
with a thickened intine. They characteristically have a single exit papilla.
Graminae (Poaceae)
Grasses are all very similar in appearance: psilate, spheroidal, from 20 to
60␮m. There is much overlap in size,
and with the exception of corn (90 to
110␮m), this cannot separate genus or

ANNALS OF ALLERGY, ASTHMA, & IMMUNOLOGY

species. Grains are monoporate, with a
prominent operculum.
Compositae (Asteraceae)
Members are tricolporate, with pores
and furrows more or less prominent.
Ragweeds (Ambrosia) have short furrows with indistinct pores, while sages
have more apparent apertures. Short,
broad-based spines on ragweeds and
marshelders (Iva), longer spines on
goldenrod, sunflower, daisy (Solidago,
Helianthus, Aster, respectively). Sages
(Artemisia) without spines, scalloping.
Size is between 15 to 30␮m.
Chenopodiales
Members of the closely related amaranth and chenopod families have very
similar pollens which are periporate,
ranging from 20 to 80 pores per grain.
Pore size and number show genus and
species differences, but the overlap is
sufficient to make identification below
the level of botanical order very difficult. Grain size is between 20 and
35␮m.
Plantaginaceae
Plantains (Plantago) are periporate, but
with significantly fewer pores than the
chenopods or amaranths. Usual pore
number is between 6 to 11. Size is
between 20 and 30␮m.
Betulaceae
The birch family has tri- to pentaporate
grains, with distinct pore-associated
findings such as annuli, aspidae, and
arci. Birch (Betula) usually has three
pores, while alder has 4 or 5. Size is
between 20 and 35␮m. Alder (Alnus)
with distinct oncus and arci.
Fagaceae
The beech family has tricolpate or tricolporate members, ranging from 10 to
15␮m (chestnut, Castanea) to 25 to
40␮m (oak and beech, Quercus and
Fagus). Shapes are from prolate to triangular in polar view.

VOLUME 80, FEBRUARY, 1998

Aceraceae
The majority of Acer species are tricolpate, with large furrows, and a striate surface. Boxelder (Acer negundo)
is tricolpate with a rugulate texture.
Vine maple (Acer circinatum) is tricolporate. Grains range from 25 to 40␮m
in size.
Juglandaceae
Walnuts and butternuts (Juglans) are
periporate, with 10 to 15 pores on the
equator and one hemisphere (heteropolar). Pores are aspidate with indistinct
onci. Hickory and pecans (Carya) are
usually triporate with pores evenly
spaced close to the equatorial plane.
Large oblate grains ranging from 35
to 55␮m.
Oleaceae
Grains of ash and olive (Fraxinus and
Olea) are tri- to tetracolpate, with short
furrows. Surfaces are finely or
coarsely reticulate, respectively. Size
varies from 20 to 30␮m.
Salicaceae
Cottonwood and aspen (Populus) have
inaperturate grains, while willows
(Salix) are tricolpate. Willows have a
reticulate surface and are between 10
and 20␮m. Populus species have a
granular texture, and are larger, between 20 and 35␮m.
Ulmaceae
Elms (Ulmus) are stephanoporate with
usually five pores, although ranging
from 4 to 7. Surface is wavy and convoluted. Grains are oblate with equatorial diameter 25 to 35␮m. Hackberry
(Celtis) pollens have 3 to 10 pores,
with a thick undulating, granular sexine, 25 to 40␮m.
REFERENCES
1. Lewis WH, Vinay P, Zenger VE. Airborne and allergenic pollen of North
America. Baltimore: Johns Hopkins
University Press, 1983.
2. Whitson TD, Burrill LC, Dewey SA, et

3.

4.
5.

6.
7.
8.
9.
10.

11.
12.

13.
14.

al. Weeds of the west. Jackson, WY:
University of Wyoming, 1991.
United States Department of Agriculture Forest Service. Range plant handbook. Dover Publications, New York,
1988.
Burge HA. Monitoring for airborne allergens. Ann Allergy 1992;69:9 –18.
Sheldon JM, Lovell RG, Mathews KP.
Standard technic for atmospheric
pollen testing by gravity method. In:
A manual of clinical allergy.
Philadelphia: WB Saunders Co, 1953:
363– 6.
Kapp RO. How to know pollen and
spores. Dubuque, Iowa: Wm C Brown,
1969.
Brown GT. Pollen-slide studies.
Springfield, Illinois: Charles C
Thomas, 1949:47–53.
Wodehouse RP. Pollen grains. New
York: Hafner, 1935.
Ogden EC. Manual for sampling airborne pollen. New York: Hafner,
1974.
Bassett IJ, Crompton CW, Parmelee
JA. An atlas of airborne pollen grains
and common fungus spores of Canada.
Hull, Quebec: Printing and Publishing,
Supply and Services Canada, 1978.
Smith EC. Sampling and identifying
allergenic pollens and molds. San Antonio, TX: Blewstone Press, 1984.
Smith EC. Sampling and identifying
allergenic pollens and molds. volume
II. San Antonio, TX: Blewstone Press,
1986.
Weber RW, Nelson HS. Pollen allergens and their interrelationships. Clin
Rev Allergy 1985;3:291–318.
Solomon WR, Weber RW, Dolen WK.
Common allergenic pollen and fungi.
In: Bieeman CW, Pearlman DS, Shapiro GG, Busse WW, eds. Allergy,
asthma, and immunology from infancy
to adulthood, 3rd edition. Philadelphia: WB Saunders Company, 1996:
93–114.

Requests for reprints should be addressed to:
Richard W Weber, MD
Department of Medicine
National Jewish Medical & Research Center
1400 Jackson St, Rm B103A
Denver, CO 80206

145

CME Examination
No. 008-002
Questions 1–20: Weber RW. Ann Allergy Asthma Immunol 1998;80:140 – 6
CME Test Questions
1. The pigment used to stain pollen grains in Caberla’s solution is
a. toluene blue.
b. basic fuchsin.
c. phenosafranin.
d. eosin.
e. hematoxylin.
2. The two outer layers of the
pollen wall are called the
a. ectomorph and endomorph.
b. intine and plasmalemma.
c. sexine and nexine.
d. baculum and protoplast.
e. aspis and oncus.
3. Plants that are both wind- and
vector-pollinated are called
a. amphiphilous.
b. aerobic.
c. entomophilous.
d. anemophilous.
e. anaerobic.
4. Apertures that are elongated
are
a. pores.
b. colpi.
c. operculae.
d. papillae.
e. vesicles.
5. Grasses are invariably
a. diporate.
b. tetracolpate.
c. monocolpate.
d. monoporate.
e. monocolporate.
6. Members of the Coniferales
order which have pollens with
air bladders include
a. larch, ginkgo, and Australian pine.
b. juniper, cedar, and hemlock.
c. yew, bald cypress, and
joint pine (Ephedra).
d. myrtle, heath, and Norfolk
Island pine.
e. pine, spruce, and fir.
7. A distinguishing feature of
docks and sorrel (Rumex spp.)
grains is
a. exit papilla.

146

8.

9.

10.

11.

12.

b. thin exine that frequently
splits and extrudes inner
portion of grain.
c. prominent starch granules.
d. large single furrow.
e. more than 60 pores.
Members of the Chenopodiales order (amaranths and chenopods) are periporate with
what range of pore number?
a. 4 to 11
b. 3 to 15
c. 12 to 20
d. more than 60
e. 20 to 80
“Stephanoporate” refers to
what attribute?
a. arrow-headed surface ornamentation
b. pores found within furrows
c. crown-like string of pores
around the grain equator
d. ⬎20 pores
e. ⱖ4 furrows aligned around
grain equator
The sexine of the pollen grain
a. may be composed of a tectum, series of columns, and
foot layer.
b. is the origin of the pollen
tube.
c. is the outer portion of the
intine.
d. contains the pollen’s nuclear material.
e. is susceptible to acetolysis.
Pollen grains that have no
pores or furrows are called
a. psilate.
b. operculate.
c. oblate.
d. percolate.
e. inaperturate.
Plantain pollen may be differentiated from amaranth pollen
by
a. being pericolpate rather
than periporate.
b. having bulging, granular
pores.
c. being triporate.

13.

14.

15.

16.

17.

18.

d. having fewer pores, 6 to 11
rather than ⬎20.
e. having pores limited to one
hemisphere.
Grains being very elongated
are
a. called perprolate.
b. have a P/E index of ⬍0.5.
c. called peroblate.
d. called echinate.
e. called obstinate.
Bald cypress or redwood pollens may be distinguished
from cedar pollen by
a. having two air bladders.
b. being monoporate.
c. having single exit papillae.
d. possessing a single vesicle.
e. being tetrads.
A triporate grain with prominent annulus, aspis, and oncus
is characteristic of which of
the following pollens?
a. broad-leafed cattail
b. mountain cedar
c. aspen
d. plantain
e. birch
What is an annulus?
a. a shield-like thickening extending away from a pore
b. a ring-like thickening or
thinning around a pore
c. a string of pores around the
equator of a grain
d. an aperture filled with debris
e. arrow-shaped surface ornamentation
A pollen grain with surface
patterns assuming a net-like
appearance is called
a. reticulate.
b. rugulate.
c. psilate.
d. pronate.
e. obfuscate.
Walnut pollen may be distinguished from sweetgum pollen
by
a. walnut has bulging pores.

ANNALS OF ALLERGY, ASTHMA, & IMMUNOLOGY

b. sweetgum has 40 to 60
pores compared to ⬍20 for
walnut.
c. walnut is heteropolar with
pores in one hemisphere.
d. walnut is tricolporate.
e. there are no distinguishing
characteristics.
19. Surface ornamentation that is
warty or bumpy is called
a. gemmate.

VOLUME 80, FEBRUARY, 1998

b. scabrate.
c. clavate.
d. echinate.
e. verrucate.
20. Cottonwood and grass pollens
may be distinguished from
each other by all but which of
the following criteria?
a. In certain locales cottonwood pollinates earlier
than grass.

b. While both are subspheroidal, cottonwood is inaperture while grasses are monoporate.
c. Cottonwood has a rugulate
to granular texture while
grasses are psilate.
d. Cottonwood is triangular
while grass is perprolate.
e. Grass has an operculum.

147

Instructions for Category I CME Credit
Certification. As an organization
accredited for continuing medical education, the American College of
Allergy, Asthma, & Immunology
(ACAAI) certifies that when the
CME material is used as directed it
meets the criteria for two hours’
credit in Category I of the American
College of Allergy, Asthma, & Immunology CME Award and the Physician’s Recognition Award of the
American Medical Association.
Instructions. Category I credit can
be earned by reading the text material,
taking the CME examination and recording the answers on the perforated
answer sheet entitled, “Continuing

Medical Education,” which can be
found after the examination.
Please record your ACAAI identification number and the quiz identification number in the spaces and scanning
targets provided on the answer sheet.
Your ACAAI identification number
can be found on your ACAAI membership card, nonmembers of the College will be assigned an ACAAI identification number and this should be
left blank on the answer sheet. The
quiz identification number can be
found at the beginning of the CME
examination.
Use a No. 2 or soft lead pencil for
marking the answer sheet. You may

erase but do so completely in order to
prevent computer reading errors. Your
ACAAI identification number and quiz
identification number will be used to
record your credit hours earned on the
CME transcript system. No records of
individual performance will be maintained.
Tear out the perforated answer sheet
and print your name and address in the
spaces provided. Return it within one
month after the Annals is received to
the American College of Allergy,
Asthma, & Immunology, 85 West Algonquin Rd, Suite 550, Arlington
Heights, IL 60005. Answers will be
published in the next issue of the Annals of Allergy, Asthma, & Immunology.

Answers to CME examination—Annals of Allergy,
Asthma, & Immunology, January 1998 (Identification No
008 – 001) Vaswani SL and Creticos PS. Metered dose
inhaler: past, present, and future. Ann Allergy Asthma Immunol 1998;80:11–23.
1. e
7. e
13. e
19. e
25. b
2. c
8. a
14. d
20. c
26. c
3. b
9. e
15. e
21. b
27. e
4. a
10. b
16. c
22. e
5. b
11. b
17. e
23. c
6. b
12. c
18. a
24. c

148

ANNALS OF ALLERGY, ASTHMA, & IMMUNOLOGY

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