220 Barratt. — A Contribution to our Knoiv ledge of the 
dichotomy of a vegetative axis. One of the sporelings of E . limosum , grown 
in culture, was found to have a forked primary axis. Only one such case 
was seen, the forking of the axis taking place at the level of the fifth node. 
The specimen was cleared and stained with ammoniacal fuchsin so that the 
vascular strands stood out clearly. 
It may be seen by reference to Text-fig. 17, that the vascular strands 
of the two branches run for a short distance 
as separate systems in the partially fused 
stem, and two nodes with the intervening 
internode are involved in the adjustments 
of the vascular system. The changes so 
necessitated include a reduction of six 
strands to three, and this takes place in 
two stages. The normal number of leaves 
for the sporeling is three, but at the node 
near the point of forking four appendages 
are present. The vascular system of the 
two branches shows greater independence 
at this region than do the external tissues ; 
there are in fact two distinct vascular 
cylinders, and a separate nodal organiza- 
tion is present for each branch. Each of 
these supplies traces to a pair of leaves. 
In each case the three bundles of the 
branch are continued by two in the inter- 
node below. The reduction is effected by 
two bundles approximating immediately 
above the node and linking up with the 
same group of nodal tracheides. At the 
node below the four strands, two from 
each branch are similarly replaced by three 
in the next internode. It may be pointed 
out that this simple method of varying the 
number of bundles in adjoining internodes 
is that normally followed in ordinary shoots. 
It is evident from the facts described 
above that this is not a case of vigorous 
development of a lateral branch, but a true forking of the primary axis. 
The Structure of the Cone. 
A careful and detailed account of the structure of the cone of four 
species of Equisetum has been given by Lady Isabel Browne (1, 2). Cones 
of each of these species were cut into series of transverse and longitudinal 
Text-fig. 17. Diagram illus^ 
Hating the vascular system of the 
sporeling of E. limosum with the 
forked axis. The difference in level 
of the two nodes in the common axis 
is real and not due entirely to per- 
spective. 
