Lycopodiales. 191 
the xylem. Of these two types the banded one is on the whole 
characteristic of creeping stems, and the other of tropical forms. 
It should be added that, according to Mr. Jones’ researches, the 
protoxylems of the banded types of stele continue to increase by 
fission, while, in some cases, branches show a reduction to the 
tetrarch type of the young stem. Mr. Jones considers that these two 
types represent two lines along which the development of the vascular 
structure of tne genus has proceeded (14). He does not seem to 
contemplate the derivation of one from the other. It seems clear 
that the banded type of stele, was, in the phylogeny, evolved from 
an exarch protostele, with projecting angles like those found in the 
young stem. These protoxylems seem at first to have been three or 
four, and with their increase in number the phloem seems to have 
increased also, and to have broken up the xylem. L. selago seems 
to have retained a rather primitive condition, the protoxylems 
being few, not more than seven, and the phloem not having split up 
the xylem completely, as the latter still forms a solid mass in the 
centre of the stem. Lycopodium tetvagonum may be even more 
primitive, for there are only four protoxylems, but this species was 
only cursorily examined by Mr. Jones. Of Lycopodium alpinum, Mr. 
Jones says “there is a great tendency to form phloem patches or 
phloem islands ; and in other respects, notably the irregular differ¬ 
entiation of the xylem near the apex, it forms a connecting link 
with the second group of Lycopods, .... which is characterized by 
the separation of distinct phloem islands ” (14). Mr. Jones notes 
a similar tendency in L. senatum. These facts seem to the present 
writer to indicate that the type of stem in which phloem and 
xylem are intermingled arises by the greater development of the 
xylem in a banded form, until the wood, spreading in most 
directions, come to surround the phloem. Indeed it is difficult to 
to see otherwise how the patches of phloem came to be enclosed 
by xylem. The irregularity of these phloem islands show that they 
do not correspond to the “ internal phloem” found in solenostelic 
Perns and recorded by M. Bertrand in Phylloglossum. Mr. Jones 
merely states that “ the phloem differentiates as isolated groups 
which break up the continuity of the xylem ” (14). This is no doubt 
a very good description of the ontogenetic process, but it does not 
explain the phylogeny satisfactorily. 
The fructifications are always homosporous; they may be 
definite strobili, as in some species of Lycopodium and in Phyllo¬ 
glossum, or the fertile and sterile leaves may be essentially similar 
