332 MORPHOLOGY OF GYMNOSPERMS 



seven to eleven in Podocarpus coriacea (69). This is a meager record, 

 but it probably expresses the variability and range in number. There 

 are four neck cells in Phyllodadus (174); but in the Podocarpus 

 investigated the number varies from two to twenty-five, the most com- 

 mon condition being three tiers of cells with four cells in each tier. 

 This extreme variability seems to hold some relation to the arrival of 

 the pollen tube, which permits an almost indefinite growth of the 

 neck or does not allow it to extend beyond the two-celled stage. 



Among the Taxineae the number of archegonia has the same range 

 (one to eleven), being one (in one case two) in Torreya taxifolia (loi), 

 two to four (usually three) in Torreya calijornica (99), two to five 

 (usually three) in Cephalotaxus Fortunei (124), four in Cephalotaxiis 

 drupacea (130), and five to eleven in Taxus. The number of neck 

 cells varies from two to six, always in one plane: two in Torreya 

 taxifolia, two or three in Cephalotaxus drupacea, two to five in Cepha- 

 lotaxus Fortunei, and four to six in Torreya calijornica. Such ranges 

 in the number of archegonia and in the number of neck cells, 

 even within a genus, indicate that such numbers have very little 

 significance. 



The comparative development of the megaspore membrane in 

 Coniferales was referred to under Pinaceae (p. 271). The Taxineae 

 are peculiar in being the only tribe in which this membrane is really 

 a negligible feature, developing none of the structure observed in 

 the other tribes. If Thomson's conclusions (108) are true, this 

 indicates that, so far as this feature is concerned, the taxads are the 

 most recent of the conifers. Among the Podocarpineae, at least as 

 evidenced by P/ir//o<:/a(/w>y {1^4), Dacrydium (174), Microcachrys (164), 

 and Saxegothaea, there is a megaspore membrane of the usual two- 

 layered type. 



Torreya furnishes a conspicuous illustration of a seed with " rumi- 

 nated endosperm" (figs. 382, 383). In a smaller degree this feature 

 appears in the seed of Phyllodadus (especially in its early stages) 

 and of the araucarians; but its extreme expression is exhibited by 

 Torreya. In the study of Torreya taxifolia (loi) an opportunity 

 was given to investigate this so-called "rumination." In ordinary 

 seeds the endosperm invades the surrounding tissue more or less 

 uniformly, in the case of most gymnosperms obliterating most of the 



