SECONDARY PROTHALLUS : SUSPENSOR 369 



corresponding male structure, purely endogenous. A few 

 ovaries (ovy) are formed on it, each consisting of a short 

 neck, an ovum, and two canal-cells afterwards converted into 

 mucilage : there is no venter, and the neck consists of only 

 two tiers of cells. 



The oosperm divides by a plane at right angles to the 

 neck of the ovary, forming the earliest or two-celled stage of 

 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 (.?/), 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. 88, A and c). Both 

 are to be considered as abbreviated shoots consisting of an 

 axis bearing numerous sporophylls (sp. pJi). Frequently, as 

 in the pines, several male cones are aggregated together, 

 forming an inflorescence^ or group of flowers. 



B B 



