109 



The zygotes subsequently sprout to long tubes, the nucleus 

 moves towards the tip of the sprouting tube. 



Generally the tip of the sprouting zygote (proenibryo) is 

 directed towards the top of the prothallium. 



On reaching the latter they push themselves between the 

 prothallium and the wall of the embryosac , finally penetrating 

 into the former. 



Subsequently the prothallium begins to grow considerably, 

 destroys the nucellar tissue and finally one sees a large pro- 

 thallium carrying on its top a small cavity, being the oblite- 

 rated fertil part of the embryosac. 



In this cavity the shrivelled zygotes may be seen while their 

 sprouting tubes have grown downwards into the prothallium. 

 Branching may here occur. On this stage of the development 

 the seeds drop. The further development of the embryo has 

 been studied by Bower. The embryosac of Gnetum Gnemon L. 

 is the morphological aequivalent of two macrospores. 



