INTRODUCTION TO CRYPTOGAMIC BOTANY. 157 



illustrated by Nageli, Kiitzing, and Braun. Several have been 

 detected in the act of forming zoospores. Their size is always 

 minute, and they are so like microgonidia, as to suggest a 

 thought that they may be connected with some larger Algae. 

 I have never had an opportunity of studying them in their 

 natural condition, and therefore cannot speak confidently of 

 their affinities. They are, possibly, as nearly related to Cotv- 

 fervacetB as to Siphonece, but technically they agree better 

 with the latter. They do not seem to me to be in the least 

 degree related to Paknellece, and the transition from Codio- 

 lum gregarium, Br.,* to Godium amphibiuTn, is so easy, that 

 I have little hesitation iu the matter. Perhaps, however, 

 Botrydium (Fig. 24) is still nearer. -f- There has already been 

 an indication of abortive rootlets in the former. In Botry- 

 dium, from its mode of growth, a still further development 

 is necessary, and thus one of the peculiar features of the 

 greater part of Siphonece is attained. Vaucheria (Fig. 22) 

 differs little from Botrydium (Fig. 24), except in the elonga- 

 tion of the subglobose cell, into a simple or branched thread. 

 VauchericB are mostly of a bright green, abound in pools, or 

 on the damp soil of fields and gardens, and form large tufts 

 on mud, whether impregnated with salt or fresh water, which 

 they tend to hold together by their numerous filaments. 

 They are by no means confined to the northern hemisphere, 



* Braun, Alg. Unicell. genera nova, tab. 1. Codiolum gregarium 

 grows on beams moistened by the spray, while Codium amphibium 

 affects turf-banks at high water mark. 



t The genus Chytridium, Braun, which is propagated by zoospores, 

 is referred, in Bot. Zeit. 1855, p. 678, by Bail, to Fungi, and Cohn seems 

 to consider it closely allied (Untersuch. tab. 16). The cells are, in fact, 

 truly parasitic, and send down a sort of mycelium into the cells of the 

 Algfe or Infusoria, on which they grow, rapidly exhausting their endo- 

 chrome. They are parasitic, for instance, on species of Euglena, Hy- 

 drodictyon, and Closterium. If this notion is well founded, we have a 

 direct transition, though other of these productions are undoubted 

 Algse, through Achlya to Mucor. The plant figured by Cienkowski, in 

 Bot. Zeit. 1866, tab. xi. as Protococcus hotryoides, is probably a Botry- 

 dium, and if so, that genus produces large resting spores and minute 

 swarming spores. It is said to grow with Botrydium (Hydrogastrum 

 gramdatum), and is certainly no Protococcus. 



