338 



MORPHOLOGY OF GYMNOSPERMS 



into the nucellus. Torreya calijornica is said to differ in that male 

 cells are not formed, but the two male nuclei are invested by the 

 general cytoplasm of the body cell, and with no inequality (99). 



In Taxus the microspore is shed in the uninucleate stage, the 

 division into generative and tube cells occurring while the spore is 

 resting on the tip of the nucellus, and the pollen tubes are in the 

 nucellus only about two months before fertilization; otherwise the 

 events are exactly as in Torreya, including the formation of two very 

 unequal male cells (fig. 387). In Cephalotaxus the first division of 



the microspore (to generative and 

 tube cells) occurs before shedding, 

 as in Torreya. Pollination occurs 

 from January to March (varying 

 with the species and the latitude), 

 but no further division occurs until 

 the following spring, when the gen- 

 erative cell divides, and the body 

 cell and stalk and tube nuclei are 

 found in the pollen tube; in fact, the 

 tube does not penetrate the nucel- 

 lus for nine to twelve months after 

 pollination (124, 130). The two 

 accounts of Cephalotaxus differ 

 as to the character of the male cells, 

 which are said to be unequal in C. Fortunei (124), and in C. 

 drupacea (130) to be represented by two male nuclei, without 

 wall-formation (fig. 388). The inequality of the cells in the former 

 species is not so great as in Torreya and Taxus; and since in- 

 equality is chiefly that of the cytoplasm rather than of the nuclei, 

 the absence of wall-formation in the latter species might result in no 

 appearance of inequality. In both cases the tube reaches the female 

 gametophyte quickly (in about ten days in C. drupacea) ; and in 

 C. Fortunei it reaches the archegonium neck before the chamber 

 is formed, so that the endosperm grows up about the tip of the tube 

 and may bury the archegonia. 



The features of the male gamictophyte of Taxineae, therefore, are 

 the absence of vegetative (prothallial) cells, a feature shared with 



Fig. 387. — Taxus baccata: tip of 

 a pollen tube with the two unequal 

 male cells; the stalk and tube nuclei 

 in advance; X200. — After Belajeff 

 i33)- 



