XI 



THE HOMOSPOROUS LEPTOSPORANGIATAl 



351 



shows its primitive character. The sini^lc vascular bundle of 

 the petiole approaches the collateral type, and is much like 

 that of the cotyledon of Marattia. Stomata of the usual form 

 occur on both sides of the lamina. The development f;f the 

 stem offers no peculiarities. The apical cell is of the tctra- 

 hedral form found in the mature sporophyte. 



The root is bulky, and the apical cell relatively small, with 

 large segments, dividing less regularly than in Onodea, and on 

 the whole approaches most nearly to Botrychium. The form 

 of the apical cell is like that of Onodea or Botrydiium, and is 

 interesting because in the later roots this is replaced by another 

 form, so that this would indicate that the three -sided form 

 found in so many cases is the primitive condition. The 

 vascular bundle is diarch. 



The foot is very large, and 

 while formed originally from the 

 upper hypobasal quadrant, it en- 

 croaches more or less upon all 

 the others. Very early its cells 

 cease to show any regular order 

 in their divisions, and divide more 

 slowly than the other cells of the 

 embryo, so that they become de- 

 cidedly larger. The cells lose 

 much of their protoplasm as they 

 increase in size, and serve simply 

 as absorbent organs. They are 



in close contact with the prothallial cells, and crowd upon them 

 until the foot penetrates deep into the prothallium, whose cells 

 it partially destroys. It is upon the large development of the 

 foot, whose outer cells sometimes are extended into root-like 

 extension like those in Anthoceros, that the young embryo is 

 maintained so long at the expense of the prothallium. 



Frequently more than one embryo begins to develop, and 

 sometimes a number of archegonia may be fertilised ; but no 

 cases were met with where more than one embryo came to 

 maturity, although it is quite possible that this may occur. 



Fig. 180. — Young sporophyte of O. Clay- 

 toniana, still attached to the prothal- 

 lium, X 6. 



