Vascular System of the Genus Equisetum . 
203 
External Morphology of the Young Plant of 
E Q UISE TUM A R VENSE. 
As already stated, the young plant of Equisetum appears above the 
level of the prothallus about eight weeks after the sowing of the spores. 
The young sporophyte consists of a slender primary stem^continued 
below as a thin elongated root. At the level of the prothallus the first 
node is found bearing two or three leaves, their bases fused into a sheath 
and their distal parts free. Just below the level of the first [node, one can 
make out the embryonical organ, the foot. It appears as a protuberance on 
one side of the axis. The primary stem continues to elongate until several 
nodes are formed, each with two or three leaves, the larger number being 
the more common. The number of nodes formed by the first shoot is very 
variable, depending largely upon the general strength and external condi- 
tions of the young plant (PI. VI, Fig. 1, a-g). 
At a very early stage in the latter’s development, a bud is formed 
which gives rise to the first branch. It appears below the first node on the 
side remote from the foot, pushing its way out below the leaf-sheath. Its 
position on the axis varies considerably, as may be seen by reference to 
PI. VI, Fig. 2, a and b ; sometimes it is situated at a considerable distance 
below the attachment of the leaves and sometimes almost at the node. 
This bud, on emerging from the primary axis, takes a sharp turn down- 
wards before ultimately taking the upward course of an aerial stem. 
Before the young branch makes its way through the cortex of the primary 
axis, it gives rise to an adventitious root whicffimmediately grows out into 
the soil. 
Other lateral buds may be developed sparingly at the upper nodes of 
the primary stem, but these develop much later if at all. 
The secondary axis, in its turn gives rise to a lateral bud with its 
associated root, and this process may be repeated until normally three 
or four upright shoots have appeared. There is a tendency for the later- 
formed shoots to be longer and more robust, with a gradually increasing 
number of leaves at the nodes (PI. VI, Fig. 1, a-g). There is, however, no 
great regularity in this last respect, the second shoot showing generally 
three leaves, and the third and fourth exhibiting four leaves in a whorl. 
According to Jeffrey ( 4 ) as many as 12 erect shoots are produced in 
E. hiemale before the first rhizome makes its appearance, but in these 
cultures of E. arvense the number of aerial shoots has never exceeded five 
and the majority show three. The fate of the later-formed branches is 
dependent upon the conditions under which the sporelings are reared. In 
the plants resulting from thinly-sown spores, three aerial shoots were 
generally formed, and the fourth and fifth were destined to be rhizomes. 
The latter elongate very quickly and grow horizontally through the soil, 
