288 NOSTOCHINEJE. 



2. NOSTOC COMMUNE Vaucll. 



Plate LXXIV. Fig. 2. 



Char. Frond terrestrial, expanded, membranaceous, plaited, 

 waved, or curled; olive green, shining, and irregular in 

 form. Filaments thick, beautifully moniliform. Repro- 

 ductive cells large, either attacked to the filaments, or lying 

 scattered throughout the frond. 



Nostoc commune Vauch., Hist, des Conf. p. 223. pi. xvi. 

 f. 1. Tremella Nostoc, Eng. Bot. t. 461. Tremella ter- 

 restris Dill., Muse. p. 52. t. 10. f. 14. ; Harvey in 

 Manual, p. 183. ; Meneghini, Monographia Nostochine- 

 arum Italicarum. 



Hob. (i Gravelly soils, garden walks, rocks, pastures, &c. ; 

 very common in autumn and winter." 



The filaments are large, exactly moniliform, flexuous, and 

 copious, with here and there an enlarged reproductive cell of 

 an exactly spherical form. These enlarged cells occur either 

 in the course of the filaments, are terminal, or lie detached in 

 the mucous matrix of the frond. Some writers have laid 

 great stress, in their descriptions, upon the fact of these 

 globules being so frequently terminal. This position of them 

 has nothing to do with the developement of the species, but 

 arises from the thread of which they formed a link having 

 separated from one side of them a step preparatory to their 

 being altogether cast off by the filaments. 



u In prima tantum hujusce speciei estate deprehendenda 

 est interior substantia aquosa-gelatinosa, qua cito elapsa 

 frons excavata potius quam vesicaeformis efficitur, stratum 

 enim periphericum, ratione habita cavitate interiori, multo 

 crassius est in caeteris omnibus speciebus." Menegh. 



The only species with which there is any danger of con- 

 founding Nostoc commune are, N. cceruleum and N.foliaceum. 

 The filaments of N. commune correspond in size and appear- 

 ance very closely with those of N. cceruleum, but the external 

 characters are altogether distinct ; the contrary is the case 

 with N. foliaceum, the external characters resembling those 



