LESS, xxx EMBRYO AND SUSPENSOR 373 



the polyplast. The upper cell undergoes further division, 

 forming an elongated structure, the suspensor (dotted in c) : 

 the lower or embryo proper (emb) is forced downwards into 

 the secondary prothallus by the elongation of the suspensor, 

 and soon passes into the phyllula stage by the differentiation 

 of a stem-rudiment (si), two cotyledons (<:/), a foot, (/) and 

 subsequently of a root. 



A further reduction of the gamobium is seen in Selagi- 

 nella : both male and female prothalli are quite vestigial, 

 never emerging from the spores : and the spermary and 

 ovary are greatly simplified in structure. 



GYMNOSPERMS 



Such common Gymnosperms as the pines and larches 

 have the character of forest trees, the stem being a strong, 

 woody trunk. The numerous, close-set branches bear small, 

 needle-like leaves, and the root is large and extensively 

 branched. 



On the branches are borne structures of two kinds, the 

 male and female cones or flowers (Fig. 87, A and c). Both 

 ar.e to be considered as abbreviated shoots consisting of an 

 axis bearing numerous sporophylls (up. p/i). Frequently, as 

 in the pines, several male cones are aggregated together, 

 forming an inflorescence, or group of flowers. 



In the male cone (A) the sporophylls (stamens, sp. ph. $ ) 

 are more or less leaf-like structures, each bearing on. its 

 under or proximal side two or more microsporangia (pollen- 

 sacs, mi. spg). The mother-cells of these divide each into 

 four microspores (pollen-grains), which are liberated by the 

 rupture of the microsporangia in immense quantities. The 

 microspore (B) is at first an ordinary cell consisting of proto- 

 plasm with a nucleus and a double cell-wall, but upon being 



