342 
the base of the colyledon. The position of this cambium is 
not fixed, as Poirault (25), van Tieghem (33), and Holle (18) 
have already pointed out for several other species of Botrychium. 
Beginning immediately under the epidermis, it proceeds centri- 
petally. This cambium seems to serve a double purpose. 
Campbell (9), who investigated B. virginianum, sees in it a 
wound cork, formed at the base of the leaf before and after 
this is thrown off. 
The fact that the cork is formed long before the leaf is thrown 
off seems to indicate that this cannot be the only cause. Perhaps 
the first periclinal divisions occur in response to the outside 
resistance of the prothallus. In that case these divisions would 
promote indirectly the liberation of the young sporophyte from 
the prothallial tissues. 
Another cambium, or rather irregular cambial activity, occurs 
in the pericycle (Fig. 9). Because the pericycle is in many 
Botrychia the place where the secondary xylem is formed, it 
would not be too bold a hypothesis to assume that the cambial 
activity in the xylem is an initial stage of the secondary growth 
of the stele. 
The cotyledon pushes out from the upper surface of the 
prothallus at a later stage than the first root. Ît is a cone- 
shaped body, which surrounds the second leaf with a sheath. 
The sheath is open at the ventral side, thus forming two 
stipulae, as in B. virginianum (19). The cardinal difference 
with this form, however, lies in the position of the leaf-initial. 
In B. virginianum it is situated near the base of the cone- 
shaped cotyledon; in B. obliquum its place is at the top of the 
cone. In this connection B. obliquum holds an intermediate 
position between B. lunaria and B. virginianum. 
It will be shown later, however, that notwithstanding the 
similarity in the position of leaf initials in B. lunaria and 
B. obliquum, there still exist important differences in the ana- 
tomy of the young bud. 
