SPERMATOPHYTES 



223 



a very prolonged process. Probably in no case is the period between the 

 first appearance of the ovule and the shedding of the seed less than two 

 growing seasons; and in some cases the seed is not shed until the third 

 season after the ovule appears, pollination taking place during the second 

 season. 



Female gametophyte. The development of the female gametophyte 

 proceeds as in the previous groups, until an extensive endosperm is 

 formed. At least two distinct regions of the endosperm are always evi- 

 dent; namely, a region of smaller 

 cells towards the micropyle, in 

 which the archegonia develop, and 

 a deeper region of larger cells, 

 which functions as a nutritive 

 region. 



Archegonia. The archegonia 

 range in number from one to sixty, 

 the usual numbers among the 

 Abietineae being three to five. In 

 the Taxodineae and Cupressineae 

 an archegonium complex is organ- 

 ized; that is, a group of archegonia 

 is invested by a common arche- 

 gonial jacket and has a common 

 archegonial chamber (figs. 491, 

 492). The necks of the archegonia FlG - 493- Archegonium of Pinus, 

 are remarkably variable in the showing two neck cells the central cell 



* (whose nucleus is just about to divide to 



number of cells, ranging from the form ventral canal and egg nuclei), and the 

 ordinary two-celled neck to that archegonial jacket. After COULTER and 

 in Pinus, which consists usually CHAMBERLAIN - 



of two tiers with four cells in each tier, but may reach four tiers with 

 as many as sixteen cells in each tier. In the Abietineae a definite 

 ventral canal cell is formed (fig. 493), but in Taxodineae and Cupres- 

 sineae only a ventral nucleus appears (as in Taxaceae) ; while in Arau- 

 carineae the situation is unknown. 



Male gametophyte. The male gametophyte is quite variable as to 

 the number of vegetative (prothallial) cells, but the condition is usually 

 constant in each tribe. In Abietineae there are two vegetative cells, 

 both of which are ephemeral (figs. 494-500) ; in Taxodineae and Cu- 

 pressineae there are no vegetative cells (as in taxads); while in Arau- 



