242 Mr. G. H. K. Thwaites on Cystocoleus. 
chrome of Chroolepus. The investing sheath is similar in cha- 
racter to that of Rhizonema interruptum, Eng. Bot. Supp. t. 2954, 
but the cells composing the latter are not at all opake. Delicate 
root-like appendages are given off from the sheaths of both spe- 
cies: indeed the analogy between these two species is curious, 
where the affinity is not very close. | 
It is interesting to observe in these minute plants a parallel 
and simultaneous growth of an internal filament and an investing 
sheath, each in some measure independent of the other and re- 
presenting separate systems of cellular development. This will 
assist, I believe, to throw light upon the real structure of the 
apparently homogeneous gelatinous sheaths with which many of 
the lower plants are furnished. 
Professor Harvey has placed provisionally in the genus Chroo- 
lepus some other minute species of a dark colour and having an 
external resemblance to the present plant: that excellent bota- 
nist, however, at the same time remarks that they will probably 
prove to be fungi. Chroolepus? Arnottii, Harv., for a specimen 
of which I am indebted to the kindness of Professor Harvey, is 
considered by Mr. Broome identical with the Torula conglu- 
tinata of Corda, and in this opinion I quite agree with him. It 
is properly an Antennaria. The present plant has nothing to do 
with the genus Helminthosporium, though some species of that 
genus has evidently been confounded with it by Capt. Carmi- 
chael and others. 
Chroolepus and Cystocoleus form with the genus Cenogonium, 
Ehrenb., a small natural group, which it is difficult to locate in 
either of the principal. divisions of cryptogamic plants. In the 
structure of their filaments they exhibit an affinity to the Alga, 
whilst they resemble the Lichens in the kind of situations in 
which they are found growing. Cenogonium has, moreover, 
apothecia very like those of a Lichen. Professor Kitzing has 
grouped together the genera Chroolepus, Chantransia and 
Chlorotylium, constituting of them his family Chantransiee, and 
arranging them amongst the Alge near the Draparnaldiee. 
EXPLANATION OF PLATE VIII. B. 
Fig. 1. Filament of Cystocoleus ebeneus, with root-like appendages. Mag- 
nified 270 linear. 
— 2. Apex of a filament, in which the development of the investing sheath 
has been arrested, and exhibiting the internal filament like that of 
Chroolepus. Magnified 270 linear. 
— 3. Portions of investing sheath. More highly magnified. 
