46 



THE OPHIOGLOSSALES 



in the mid-region of the sporophyte (fig. 27, C), the only difference noted is a slightly 

 greater development of the xylem. The section of the root (fig. 27, D) presents 

 almost exactly the same appearance as that of the leaf. Whether we should call the 

 root bundle "monarch" or "collateral" is merely a question of terms. In the mid- 

 region the endodermis can be clearly seen, and it is then evident that the xylem is 

 separated from it by a single layer of pericycle cells. 



Fig. 28. 



A. Archegonium of Botrychiunt virginianum, containing a two-celled embryo. X275. 



B. Four longitudinal sections of an embryo with 7 cells. X275. 



THE EMBRYO OF BOTRYCHIUM. 



The following account of the development of the embryo of Botrychium is 

 based mainly upon material of 5. virgtntanum furnished me through the kindness 

 of Professor Jeffrey. 



In this species, as in the other Eusporangiatae, there is a marked increase in the 

 size of the fertilized ovum before the first division takes place. At the time of the 



Fig. 29. — Young embryos of Botrychium virginianum. 

 Longitudinal sections. X200. i i, basal wall. A. Four-celled embryo. B-D. Older stages. 



first division the ovum is generally more or less elongated, but this is not always the 

 case. This elongation is less marked in B. lunaria (fig. 36), while in B. obliquum 

 the ovum becomes much elongated before the first division occurs (see Bower 9, 

 fig. 266). 



