152 
PHARMACEUTICAL BOTANY 
fill two cavities, one on either side of the connective. The micro- 
spores or pollen grains at first show only a thin clear cellulose layer, 
but from this, by a differentiation of the exterior film, the exospore 
layer becomes cut off. This becomes cuticular. The cellulose inner 
layer ( endospore ), remains unaltered. In the development of the 
exospore, one to several deficiencies are usually left in it through 
which the endospore may protrude later as the rudiment of the pol- 
len tube. 
Attachment of Anther. — The attachment of the anther to the fila- 
ment may be in one of several ways, as follows: 
Innate, attached at its base to the apex of the filament. 
Adnate, adherent throughout its length. 
Versatile, when the anther is attached near its center to the top 
of the filament, so that it swings freely. The adnate and versatile 
are introrse when they face inward, extrorse when they face 
outward. 
Pollen. — The pollen grains or microspores vary in form for differ- 
ent species and varieties and while they are averagely constant for 
these, nevertheless many exceptions have been recorded. The fol- 
lowing are some of the commoner forms: 
Four Spore Daughter -cells, hanging together as in the Cat Tail 
( Typha ) forming a pollen grain. 
Elongated, simple pollen grains as in Zostera. 
Dumb-bell-shaped, as the pollen of the Pines. 
Triangular , as in the ( Enotheras . 
Echinate, as in the Malvaceae. 
Spherical, as in Geranium, Cinnamon and Sassafras. 
Lens-shaped, as in the Lily. 
Spinose, as in the Composite. 
Barrel-shaped, as in Polygala. 
Under the microscope the immature pollen grain generally consists 
of two membranes, an outer firmer one called the exospore , which 
may be variously marked and which possesses deficiencies in the 
form of “pores ”or “ clefts,” andan inner delicate cellulose membrane 
called the endospore, which surrounds a protoplasmic interior in 
which are imbedded a nucleus, oil droplets and frequently starch 
or protein. 
