i6o 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, Wistaria 

 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 veiy 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 Plania 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: 



W^aten 9.19 



Nitrogen 4.81 



Ash 3.81 



After drying thoroughly he found: 



Nitrogenous Matter 31.63 



Non -nitrogenous G4.36 



Ash 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 



