postelsta 67 



limited space. During this period of 

 its existence the plant lives wholly as 

 a parasite, nourishing itself upon the 

 food-materials stored in the adjacent 

 tissues. It is a true parasitism fostered 

 by the parent for the good of the 

 species. It is not a condition originat- 

 ing in seed-plants, but traces back to 

 the first simple Bryophyte which re- 

 tained the oosperm within the female 

 reproductive organ and nourished the 

 young sporophyte from food-materials 

 of its own accumulation. The extra- 

 seminal life is the continuance of a 

 habit which the sporophyte later de- 

 veloped of assuming an independent 

 vegetative condition after the tissue of 

 the gametophyte had been exhausted. 

 The retention of the female gameto- 

 phyte within the sporangium marks the 

 origin of the seed-habit, but the para- 

 sitic habit of the sporophyte was al- 



