THE GAMETOPHYTE 



123 



proterandrous and not dioecious, as might be supposed from a casual examination. 

 The margins of the large prothallium are more or less irregularly lobed and it is not 

 unlike that of Osmunda, but as in the other Marattiacea; the wings of the prothal- 

 lium are several cells in thickness near the midrib, and only at the extreme edge 

 are they reduced to a single cell in thickness. 



The full-grown prothallia are a centimeter or more in length and nearly as 

 broad. One very large specimen was found (fig. 90, F). This bore a young sporo- 

 phyte with two fully developed leaves, and the prothallium measured nearly 2.5 

 centimeters in length by 1.75 in extreme width, and was also very thick. A second 

 archegonial cushion was present, but whether this was due to a forking of the original 

 apex, such as not uncommonly occurs in Marattia and Angiopteris, was not deter- 

 mined, although this was very probably the case. 



Fig. 90. — Kaulfu^ia asculifolia Bl. 



A. Young gametophyte. .4. 



B. Apex of A, showing the antheridia, $ N 10. 



C. An older gametophyte, with archegonia, ^ . X4 



D. Apical region of an older gametophyte; a, apical cell. 



K. An older gametophyte, with young sporophyte attached, cot, cotyledon; 

 r, root. 



F. Two views of a large gametophyte, with attached sporophyte, natural size. 



G. Rhizoid. X50. 



H. Apex of rhizoid, more highly magnified. A single nucleus only is present. 



The rhizoids are stout and they have thick but quite colorless walls. They 

 o'ten show apparently transverse septa and the extremity is not infrequently forked 

 (fig. 90, H). An examination of these rhizoids shows that these septa are not the 

 result of true cell division, as only one nucleus can be found in the whole rhizoid. 

 As the nucleus is large and conspicuous, and only one can be seen, it looks as if the 

 formation of septa is secondary and not connected with cell division. 1 he structure 

 of the apex of the prothallium is exactly as in Marattia and Angiopteris. The 

 apical meristem shows the usual row of marginal initial cells, of which one (fig. 90, 

 D, x) is often somewhat larger than the others and may possibly represent a single 

 apical cell. 



