i 9 4 
Lady Isabel Browne. 
the type of L. Phlegmaria. Concerning it Dr. Lang writes : “ This 
form suggests comparison with the modification of the prothallus of 
L. selago referred to above, which was seen to arise by the 
localization of growth in one part of the meristematic zone . . . . ” 
(15). Further on Dr. Lang sums up the inter-relationships of the 
prothalli very lucidly in the following words:—“The similarity 
in ground plan of the prothalli would appear rather to indicate that 
they are all more or less profound modifications of a type not unlike 
that of L. cernuutn. The two forms of prothallus found in L. selago 
give the clue to the more specialized saprophytic types, which, in 
the deeper growing subterranean species, retain the radial symmetry 
while becoming modified in shape. On the other hand the type of 
prothallus growing in rotting wood (that of L. Phlegmaria) has lost 
the radial symmetry and consists of cylindrical but more or less 
clearly dorsiventral branches. The variability of several characters, 
such as the presence or absence of leaf-lobes, the distinctness of 
the primary tubercle, and the passage from radial to dorsiventral 
symmetry within the limits of the L. cernuum- type, when taken in 
conjunction with the variety of form of the L. selago prothallus 
appears to justify such a view as that suggested above” (15). 
Professor Thomas’ discovery, since the above was written, of the 
prothallus of Phylloglossuni (22) strengthens Dr. Lang’s view of 
the primitiveness of the L. ceruumn-type of prothallus, for the 
reappearance of a character in an allied genus increases the 
probability of that character being primitive. 
The affinities of the Lycopodiacese with the other orders of 
the phylum do not appear to be close. From the Lepidodendraceae 
they differ in the absence of a ligule and of secondary growth in 
thickness, in their constant homospory, and in the fact that their 
fructifications are not always definitely strobiloid, as are those 
of the Lepidodendraceae (except perhaps Piuakodendron). Mr. 
Jones (14) and Mr. Hill (13) have, however, found in the sporo- 
phylls and leaves of some species of Lycopodium, mucilage-canals, 
which the latter writer compares to parichnos. Owing to the 
small size of the leaves of Lycopodium, these parichnos are pre¬ 
sumably an ancestral character, inherited from a larger leaved 
form. Miss Sykes points out “ . . . that it is possible to regard 
Spencerites as an ancient connecting link between the old Lepido- 
dendra and the Lycopodiums, perhaps one of the first of a chain 
of genera which were to form a long reduction series” (21). 
Very striking similarities between L. cernuum and Spencerites 
