60 



a mass of spore mother cells. While this has 

 been going on the outer wall divides up by- 

 tangential walls, and so the wall of the sporan- 

 gium is now two cells in thickness. 



(4) The mother cells round themselves off and 

 become isolated from each other. Each mother 

 cell divides up into four daughter cells, each 

 of which is tetrahedrally shaped : they retain 

 their relative position until mature. An im- 

 mense number of these small spores is thus 

 produced. The tapetum persists until the 

 spores are ripe (while in ferns it is absorbed 

 during the formation of the spores). The fol- 

 lowing changes, called Germination^ now take 

 place while the spores are still within the 

 Sporangium: — 



(a) At one end of the spore a small cell is cut oif 

 by a very fii'm wall. This cell has no function 

 to perform, and is called the Vegetative Cell,, 

 and may be considered as a rudimentary 

 prothallium. 



(b) Successive division now takes place in the 

 larger part of the spore— the whole of this 

 tissue is regarded as the Anther idium,, and 

 the central tissue becomes the Antherozoid 

 [spermatozoid) Mother Cells. 



(c) Each mother cell contains a nucleus and 

 protoplasm. The nucleus grows at the ex- 

 pense of the protoplasm, and forms a spiral 



