242 Mr. G. H. K. Thwaites on Cystocoleus. 



chrome of Chroolepus. The investing sheath is similar in cha- 

 racter to that oi 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 Canogonium, 

 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 Algce, 

 whilst they resemble the Lichens in the kind of situations in 

 which they are found growing. Ccenogonium has, moreover, 

 apothecia very like those of a Lichen. Professor Kiitzing has 

 grouped together the genera Chroolepus, Chantransia and 

 Chlorotylium, constituting of them his family Chantransiece, and 

 arranging them amongst the Algse near the Draparnaldiece. 



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 highlj' magnified. 



