494 



MOSSES AND FERNS 



CHAP. 



the writer, is intermediate in^this respect between the two. A 

 second difference is the later period at which the cell division 

 in the lower part of the prothallium is completed in 5. Kraus- 

 siana. In this species, too, no root-hairs were seen, while 

 Pfeffer observed them in S. Martensii. Finally, in the latter 

 the suspensor is much shorter and straighter than in vS. 

 Kraussiana. 



In vS. Martensii, almost as soon as the cotyledons are 



Cot. 



Fig. 259. — SelagincUa Kraussiajia (A. Br.). A, Macrospore with the prothalHum {pr), X50; B, 

 young sporophyte still attached to the spore {sp), x8 ; cot, cotyledons ; R, root ; C, upper part of 

 an older stage, X 6 ; D, a still older one showing the first dichotomy, X 4 



established, the two-sided apical cell of the stem is replaced 

 by a four-sided one, from which are then produced two similar 

 ones by the formation of a median wall, and a true dichotomy 

 of the primary axis thus takes place at once, the two new 

 branches growing out at right angles to the cotyledon. While 

 this may also occur in 5. Kraussiana (Fig. 259, D), it is not 

 always the case, and frequently the young plant remains 



