CHAPTER XXXV. 



MORPHOLOGY OF THE NUCLEUS AND SIGNIFI- 

 CANCE OF GAMETOPHYTE AND SPOROPHYTE. 



469. In the development of the spores of the liverworts, 

 mosses, ferns, and their allies, as well as in the development of 

 the microspores of the gymnosperms and angiosperms, we ha^'e 



observed that four spores are formed 

 from a single mother cell. These 



Fig. 313- 

 Forming spores in mother 

 cells (Polypodium vulgare). 



Kg. 314- 

 Spores just mature and wall of 

 mother cell broken (Asplenium bul- 

 biferum). 



mother cells are formed as a last di\'ision of the fertile 

 tissue (archesporium) of the sporangium. In ordinary cell di- 

 vision the nucleus always divides prior to the di\"ision of the cell. 

 In many cases it is directly connected with the laying down of 

 the dividing cell wall. 



470. Direct division of the nucleus. — The nucleus divides in 

 two different ways. On the one hand the process is very simple. 

 The nucleus simply fragments, or cuts itself in two. This is 

 direct division. 



471. Indirect division of the nucleus. — On the other hand 

 very complicated phenomena preCede and attend the division of 



239 



