424 Farmer and Freeman. — On the Structure and 
unfolded leaves may be easily detected as swellings on the 
rhizome in front of the one actually unfolded. They are 
perfectly ensheathed in the stipular structure just alluded to, 
and the actual arrangement strikingly recalls that met with in 
Botrychium , and, though to a less extent, that in Ophioglossum 
also. 
It will be remembered that in Ophioglossum there is 
a funnel-shaped appendage in front of each leaf, which some- 
what closely resembles an ochrea, and that this ensheathes 
all the younger leaves (which repeat the same arrangement) 
and also the stem-apex. The ochrea in Ophioglossum is 
formed by a ring-like upgrowth of the stem in front of the 
leaf ; this may be regarded as representing a foliar structure 
the insertion of which completely encloses the stem, as may 
be seen, for example, in the leaf of the Onion. In Botrychium , 
however, the sheath is somewhat simpler, and more obviously 
confined to the leaf. Holle 1 , who investigated Botrychium 
Lunaria as well as Ophioglossum , gives a good account and 
figures. Our own observations, which are illustrated by the 
diagram (PI. XXL Fig. 3), confirm him in all important respects. 
In Botrychium Lunaria the leaf-rudiment, as soon as it is 
differentiated from the apical meristem, grows much faster 
on one side than it does in length, and thus a sort of hood 
or flap is produced which extends over the apex, its edges 
fitting into a corresponding depression situated on the opposite 
side of the stem. The base of the leaf, though broad, does 
not surround the stem, and the chamber which is formed by 
the projecting flap communicates with the exterior through the 
narrow slit left between the free edge of the hood and the 
depression into which it fits. The foliar part of the leaf is 
developed from the back of the leaf-rudiment taken as 
a whole, and therefore the flap comes to lie as a sort of 
adaxial appendage of it. These relations are very difficult to 
make out in the older leaves, as the changes produced by 
growth and extension of the tissues tend to obscure them. 
Thus the blade-portion of the older, but still enfolded, leaves 
1 Holle, loc. cit. 
