676 
PROFESSOR F. 0. BOWER OR THE DEVELOPMENT AND 
of the new organs at the apex, an arrangement which is well adapted to the growth 
of the plant under circumstances which alternately favour and prevent vegetative 
activity. In the young Lycopodium the supply of nutritive materials is drawn by 
the foot from the prothallus as it is wanted by the young sporophore. It is further 
to be observed that the same difficulty has been experienced by Dr. Treub in dis¬ 
tinguishing the morphological character of some of the young organs ( l.c ., p. 130) as 
meets os also in the case of Phylloglossum: shall an outgrowth which appears not 
clearly lateral, such as that described as the first leaf in Phylloglossum, be designated 
a leaf or not? It is only to be expected that such difficulties should arise as we 
investigate plants which are low in the scale of development, and especially when 
we observe the development of their embryos. As regards the origin of the root, 
there is no doubt that in Phylloglossum it is exogenous, and that the first root is 
adventitious. In Lycopodium cernuum also the origin of the first root is compara¬ 
tively late, and it is adventitious. I cannot think, however, that the one example 
shown by Treub (Plate XVII., fig. 1) excludes the possibility of the first root being of 
exogenous origin, and it is to be observed that other figures (e.g., figs. 2, 3, 4 of 
Plate XVII.) seem rather to point to an exogenous than an endogenous origin. It 
may also be observed that the connexion of the vascular bundles of the leaves and 
root, and their absence in the tuber (“ tubercle embryonnaire ”) in Lycopodium cernuum 
correspond with the distribution of the bundles in Phylloglossum. Taken as a whole, 
and discounting the absence of the foot, and the storage of nutritive materials in the 
tuber before the development of the apex to form leaves and other organs, it may be 
said that the whole development of Phylloglossum from the tuber is strikingly similar 
to the embryonic stages of Lycopodium as described by Treub. A comparison of 
the two leads clearly to the conclusion that, provided the sporophore generation of 
Phylloglossum corresponds in its more important points to that of Lycopodium , we 
may regard Phylloglossum as a form which retains, and repeats in its sporophore 
generation, the more prominent characteristics of the embryo as seen in Lycopodium 
cernuum; it is a permanently embryonic form of Lycopod. 
Description of the Figures. 
PLATE 71. 
Fig. 1. Part of transverse section of the stalk of a mature tuber: xy= the strand of 
xylem. c indicates the position of the channel, which is in this case 
completely closed. (xl75.) 
Fig. 2. Part of a similar section : here the channel (c) is still open, (x 175.) 
Fig. 3. Peripheral part of a transverse section of a mature tuber, showing the super¬ 
ficial epidermis, with peculiarly thickened walls, and one root-hair ( h ). 
(X 130.) 
