160 Composition of Pollen. 
form the male element in plants. They are in plants what 
the spermatozoa or sperm-cells are in animals; and as the 
sperm cells are much more numerous than the eggs or 
germ cells, so pollen grains are far more numerous in plants 
than are the ovules or seeds. In Chinese wistaria, Wistarda 
Sinensis, there are, says Goodale, about 7,000 pollen grains 
to each ovule. Pollen grains are really single cells and 
have two coats; the outer is the extine which may be 
smooth, variously sculptured, or even thickly set with spines 
(Fig. 56). These spines etc., often enable us to tell the 
species of plant from which the pollen came. Usually the 
extine is perforated, though the inner wall—intine—is not. 
These perforations are also definite in number within the 
species. These holes give opportunity for the pollen tubes 
(Fig. 184) to push out after the pollen grain reaches the 
stigma of the flower. Where there are no perforations of 
the extine, the wall breaks. In some cases like orchids, 
pollen grains are held together by an adhesive substance. 
In our milkweeds we notice a similar grouping of pollen 
grains (Fig. 162) which often are very disturbing to bees 
and other insects. 
The composition of. pollen, says Goodale, is protoplasmic 
matter, granular food materials, such as starch and oil and 
dissolved food matters, sugar and dextrine, 
Dr. A. de Planta gives the following analysis of pollen 
of the hazel (B. B. Journal, Vol. 14, p. 269). He finds pro- 
toplasm, oils and starch—the important food elements. 
Before drying he found: : 
Nitrogenous Matter......cssssccsscssrsscsrerscsessrstcesscsssesaarees 31. 
Non-nitrogenous 64.36 
ANSNvs Asics dsvoaddbensee cevsssaesees os eee 4.01 
He found no reducing sugar, but did find 14.70 per cent. 
of cane sugar. 
As will be seen, pollen like our grains is rich in the 
albuminoids. Like our grains or even different specimens 
of the same grain the composition of pollen will doubtless 
