4^6 Bower.—Studies in the Phytogeny of the Fi tic ales. 
of the V has put out a process from its inner face, while there is a rounding 
off of the apex of the V so as to give a circular internal contour ; the ends 
of the divergent shanks of the V then become abstricted (see section III, 
which, however, shows that to the right still attached) ; after pursuing 
a short independent course they both end blindly. Meanwhile, the re¬ 
mainder of the leaf-strand closes into a complete circle, and in fact becomes 
a solenostele, while the sclerotic strand widens out laterally, and forms 
a slit centrally (section IV) ; higher up this widens as in the case of a 
normal leaf, and thus the secondary stolon passes off from the primary 
stolon which produced it. Section V of the series shows the parent stolon 
after the separation is complete. 
How nearly a stolon thus produced may in position and in outline 
correspond to a leaf is shown by a tangential section represented in Fig. 13 ; 
here the stolon ranks with the leaves in position and in form ; in fact 
the only feature which distinguishes it is the vascular supply, which has 
clearly the character of a solenostele. Moreover, if the origin of the ‘ trace ? 
of such a stolon be examined in a series of sections of the stock, it will be 
seen that it originates just as a leaf-trace does ; but it may be found to differ 
in form and outline from the very first (Text-fig. 5, a ), while as it passes 
outwards it assumes a protostelic structure and circular outline (Text- 
fig- 5, ^ c). 
Clearly this history of origin of a stolon differs from that previously 
described ; here the leaf appears to be completely replaced by the stolon ; 
its vascular supply is mainly taken up in constituting the solenostele, while 
the remainder terminates in blind endings right and left. In the previous 
case the leaf has an apex which is traversed by a vascular strand, but early 
arrested ; there is a difference also in the origin of the solenostele of the 
stolon from it. Without the history of development of the stolon from its 
first stages, for which the material did not suffice, it is impossible to be sure 
whether or not the apex of the leaf is ever involved, but certainly in some 
cases the origin of the stolon is on the adaxial surface at some distance 
from the apex. 1 Mettenius 2 has drawn attention to the variation in 
position of the buds in the Hymenophyllaceae, sometimes on the axis, 
sometimes axillary, and again sometimes upon the leaf-stalk itself, but 
always subtended by the leaf. The case of Plagiogyria appears to be 
of the same nature, but it plays in a region further removed from the leaf- 
base. This latter fact may be related to the closer aggregation of the leaves 
upon the shoot, and Mettenius has already discussed this point ( 1 . c., p. 625) 
in the case of the Hymenophyllaceae with crowded leaves, in which also he 
found the position of the bud to be some distance from the leaf-base. 
1 It is not possible to say how far the case of Plagiogyria corresponds to any of those examples 
worked out developmentally by W. Kuppner, Flora, 1906, p. 337. 
* Ueber Seitenknospen bei Farnen, p. 615. 
