ANATOMY OF TISSUES. 1038 
double, for example, the Lycopods and Selaginellas, although in 
these plants, the forking is not always equal. 
There are also adventive branches or buds which may occur 
at any time and almost at any place along the stem. The bundle 
system of such branches unites itself to the nearest portions of 
that of the stem. To these few facts, it may be added that in 
general, the connection between the bundle systems of branch 
and main axis is such as is best adapted to the various functions 
of the tissues concerned. 
PHANEROGAMIC STEMS. 
According to their morphological development the gymno- 
sperms should be placed next to the vascular cryptogams. The 
anatomical structure of their stems, however, corresponds to 
that of the dicotyledons, and in a comparative study of the 
anatomy of the vegetative organs of plants, the stems of 
gymnosperms and dicotyledons may be considered together, 
while the structure of the monocotyledonous stem is on an 
entirely different plan and of such a nature as to rank it next 
to that of the Pteridophytes. 
As regards the development of the respective centres of growth 
of the young embryo, it has been stated that the apex of the stem 
of vascular cryptogams consists generally of a single cell, but 
that in a few cases, occurring chiefly in the family Lycopodiaceae, 
a cluster of cells has been found to hold such a position in refer- 
ence to the stem axis that the cells composing it may be called 
apical. That is, they le about the axis in such a manner that 
each may constantly divide and give off new cells without losing 
its own position and rank. Fora long time it was supposed 
that the apex of some Conifer stems was of this nature, and 
efforts were made to prove that even here, examples might be 
found of growth from a single apical cell. If this could be 
proved it would furnish another evidence of the possibility of 
