168 lAnnean Society. [Jan. 20, 



visible in a transverse section. At a later period, when the chains 

 are ready to break up at the connecting joints, no trace of this en- 

 velope is to be detected, and the plant then exhibits the true cha- 

 racters of Nostoc. It appears indeed, fi-om the remarks of Thuret, 

 that when the threads of Nostoc are first generated from the large 

 connecting bodies, there is really such an envelope ; but this exists 

 in Nostoc, as far as is at present known, merely in the infant state ; 

 and consequently if the genus Hormosiphon is to be retained, the 

 Arctic species must be regarded as belonging to it, for no such ap- 

 pearance has been detected by Mr. Berkeley either in dried or freshly- 

 gathered specimens of Nostoc commune. It is possible that more 

 extended observation may show that this character is not of the 

 consequence attributed to it by Kiitzing ; but in the mean time Mr. 

 Berkeley characterizes these specimens as — 



Hormosiphon arcticus, foliaceo-plicatus viridis vel fuscescens, fills de- 

 mum (gelatina diiFusa) liberis. 



Fronds foliaceous, variously plicate, sometimes contracted into a 

 little ball. Gelatinous envelope at length effused ; connecting cells 

 at first solitary, then three together ; threads (which are nearly twice 

 as thick as in Nostoc commune^ breaking up at the connecting cells, 

 so as to form two new threads, each terminated with a single large 

 cell, the central cell becoming free. Of these threads and of their 

 gelatinous envelope Mr. Berkeley gives figures. 



With regard to the Thibetan Nostoc, Mr. Berkeley adds that a 

 species of this genus, as is well known, is a native of Tartary and is 

 eaten abundantly in China. There is a box of it, sent by Mr. Tra- 

 descant Lay, in the Museum of the Linnean Society ; and mention 

 is made of it by M. Montagne in the ' Revue Botanique,' ii. p. 247, 

 as having, in the form of a soup, made part of a dinner given by the 

 Mandarin Huang at Macao, to several members of the French Em- 

 bassy. The Mandarin described it as a freshwater plant, growing 

 in Tartary in streams and running water, and sold at Canton in 

 small boxes : it is highly esteemed by the Chinese, and not very ex- 

 pensive. At this time M. Montagne regarded the species as Nostoc 

 cceruleum, but specimens sent him by Mr. Berkeley proved it to be 

 distinct, and it was afterwards published in the ' Revue Botanique ' 

 under the name of Nostoc edule. Berk, and Mont., and figured by 

 Kiitzing in his 'Tabulae Phytologicce.' In the last-named author's 

 • Species Algarum,' it is said to have been gathered by Gaudichaud, 

 who, although a great traveller, was certainly never in Tartary. 

 The Thibetan Nostoc, like the Arctic, is probably quite as good as 



