380 Chandler. — On the Arrangement of the Vascular Strands 
parenchyma. It will be seen that the writer’s investigations confirm the 
results arrived at by the latter author. 
The cauline strand increases somewhat in size, but is still in the form 
of a curved band, and the second leaf-trace is formed in a manner precisely 
similar to the first, but from the other extremity of the vascular tissue 
(Figs. 91-95). Soon after the completion of the leaf-trace, a root-strand 
joins the vascular band, which quickly divides into two parts, each being in 
section an arc of xylem and phloem surrounded by a pericycle and endo- 
dermis. One of these secondary strands is considerably larger than the 
other, and from it the third leaf-trace is nipped off just as in previous cases. 
The two strands then approach one another and fuse, the junction being 
maintained for a short distance ; they soon separate again, however, and 
from one of them the next leaf-trace is formed as before, but more or less 
opposite the previous trace (Figs. 96-102). This radial arrangement of the 
leaf-traces in the young plant is of considerable interest, since the most 
striking feature of mature specimens is the dorsiventrality of the rhizome, 
the leaves being arranged in two rows on the upper surface and the roots 
confined to the lower and lateral surfaces. A root-trace soon joins one of 
the cauline strands after the exit of the leaf-trace, and then the augmented 
strand divides into two portions, one of which unites temporarily with the 
remaining original cauline bundle (Figs. 103-109) ; as before, the separation 
is connected with the formation of the next leaf-trace. 
The unusual length of the internodes makes it a matter of some little 
difficulty to clearly realize what is actually taking place in connexion 
with the formation of the leaf- traces. In spite of the fact that the 
protostelic and the subsequent amphiphloic conditions of the transitional 
region do not obtain in this fern, the somewhat simple siphonostelic (phyllo- 
siphonic) nature of its vascular system is quite obvious as soon as two or 
three leaf-traces are formed, although, as stated above, the length of the 
internodes, together with the small size of the cauline strands, makes this 
fact somewhat difficult of realization. Instead of the leaf-trace being formed 
in the normal way, we have a splitting of the vascular strand followed by 
the constricting off of a portion to form the leaf-trace. The subsequent 
fusion (really the closing of the elongated gap), followed by a new splitting, 
demonstrates the essentially siphonostelic nature of the vascular system of 
this plant. It is interesting to note that a somewhat similar series of changes 
occurs, as an exceptional circumstance, in connexion with some of the early 
leaf-traces of Aspidium falcatum (q.v.), although in this case the transi- 
tional region presents the normal protostelic and amphiphloic conditions. 
To return. The fifth leaf-trace is the first to hint at the double traces 
which are so characteristic of the mature plant. It is derived from the 
two portions of the divided cauline strand by the nipping off of a small 
concentric bundle from each ; one half of the leaf-trace is formed at 
