CONIFERALES (TAXACEAE) 



341 



Ginkgo, but in Phyllodadus the nucleus (or nuclei) becomes free. 

 As a consequence, the spores on the tip of the nucellus arc found 

 to contain three or four nuclei, one or two of which arc vegetative, 

 and the body cell. In Dacrydium (136) the generative cell is cut 



/ 



t;\ ■'■■■:■■ : I. 



392 



393 



396 



Figs. 392-396. — Pollen grains of several podocarps: stalk, body, and prothallial , 

 cells evident; fig. 392, Phyllodadus alpiiia, showing an evanescent and a persistent! 

 prothallial cell, also stalk, body, and tube cells; X950; after Miss Young (174); 

 fig- 393 1 pollen grain of Microcachrys lelragona at the shedding stage; after Thomson i 

 (163); figs. 394, 395, Saxegothaea conspicua; fig. 394, the two prothallial cells, the 

 generative cell, and the tube cell are in a line; X700; after Noren (149); fig. 395, 1 

 later stage, showing body cell, and nuclei of tube, stalk, and three prothallial cells; | 

 also several large starch grains; X700; after Noren (149); iig. ;^g6,Podocarpi<s totarra 

 Hallii; the usual condition of pollen grain at the shedding stage, containing tube J 

 nucleus, stalk and body cells, and eight prothallial cells (only four shown) derived j 

 from the two primary prothallial cells; after Burlixgame (139). 



ofif immediately after the two prothallial cells, and then it and the 

 second prothallial cell divide. In some cases {D. Bidwillli) usually 

 only the second prothallial cell divides, but in others {D. laxijoliiuip 

 and D. cupressinum) both prothallial cells divide. The result is 

 that at pollination the spore contains three or four free vegetative 

 nuclei, in addition to the body cell and the stalk and tube nuclei 



