THE MALE GAMETOPHYTE OF DACRYDIUM 



. CONTRIBUTIONS FROM THE HULL BOTANICAL LABORATORY, 99 



Mary S. Young 



(with plate xix) 



Until 1902^ when Coker (i) published a paper on the gametophytes 

 and embryo of Podocarpus, we had no account whatever of any of 

 the Podocarpincae. The fact that they are in the main forms of 

 the southern hemisphere has made it hard to secure the necessary 

 material. Coker's study was made from two cultivated trees, and 

 his results, so far as the male gametophyte is concerned, were, very 

 briefly, as follows: (i) The pollen grain contains two prothallial 

 cells; the first degenerates slowly, the nucleus of the second slips 

 out into the general cytoplasm and may divide; the first may segment. 

 (2) The mature pollen grain sometimes contains as many as six 

 nuclei, (3) There is one functional male cell formed. 



In connection with these results it is interesting to note some recent 



work on Araucarineae, In 1905 Thompson (2) found in the pollen 

 tubes of Agathis supernumerary nuclei, sometimes as many as thirteen, 

 but was not certain of their origin. In the same year he found a 

 similar condition in Araucaria, and in one instance at least, there were 

 more than thirty nuclei placed fore and aft. In 1905 Lopriore (4) 

 described the pollen grains of Araucaria BidwilUi. According to his 

 account, two lenticular cells are successively cut off from the main 



them 



The free 



central nucleus and an inner cell of the complex increase in size and 

 undergo no further divisions; they remain distinct from the others, 

 and even in the germinating tube can be recognized. One of them 

 is figured with a conspicuous envelope of cytoplasm rich in starch. 



about 



Nuclear 



about thirty-six 



free nuclei in the general cytoplasm. Lopriore interprets the cell 

 complex as representing an antheridium and considers the two large 

 nuclei as vegetative in character. The paper has been reviewed by 



180] 



[Botanical Gazette, vol. 44 



