44 NOSTOC AND COLLEMA. 



pi-oper precautions to prevent external influence. After some days 

 the sections became less transparent, and intensely green from the 

 crowding of the gonidia, which were now arranged in curved rows 

 closely rolled together into balls. Upon the upper surface of the 

 section appeared little gelatinous balls or warts, which contained 

 gonidia in rows, and gradually developed typical Nostoc forms ; 

 whilst on the edges of the sections appeared little colourless wart- 

 like masses of jelly, in which, after some time, appeared gonidia, 

 some of which developed into the typical Nostoc form, orhers into 

 true Collemoid plants. 



M. Baranetzky further states that he watched the body of the 

 section gradually change by the continual growth and increase of 

 the rows of gonidia before alluded to, and by the disapjiearance of 

 the Collemoid threads, until at last the whole mass of the tissue 

 of the lichen had been converted into a true Nostoc, which was 

 finally identified as Nostoc vesicarium, D.C. 



I have no observations of my own to offer on this subject ; but 

 think enough has been done to show not only that the Nostocs 

 proper have very close relations with the Collemoid lichens, but 

 that they are probably a peculiar phase in their life history. This 

 being the case, it may seem a superfluous work to indicate species 

 among the Nostocs. To anyone who has given much study to the 

 fresh -water algfe, the reply to this will immediately suggest itself, 

 namely, that in the present state of the science it seems impossible 

 to avoid it ; they are so commonly thrust at one by collectors, 

 amateurs, &c., are so distinct, are so often the subject of tongue and 

 pen, that they must have a name. The idea 'that attaches to the 

 term species is at present not a very definite one ; that there are, 

 however, among the Nostocs fixed forms, which do not change into 

 one another, and can readily be distinguished, I have no doubt. 

 Such forms are herein described. If they be only life stages of 

 Lichen, I have no doubt that it will finally be found that each so- 

 called species of Nostoc has its own peculiar so-called species of 

 Lichens, from which it alone springs, and into which alone it can 

 develope. It seems tome, then, that as yet no cause for abandon- 

 ing the specific names of the Nostocs has been shown, but only 

 reason to study also their relations with the various CoUema. 



SPHAGNUM TERES.— 4«^s<ro?». 



This species is described and figured by Dr. Braithwaite in 

 " Monthly Miscroscopical Journal," for July, 1874, plate 68. 



Sphagnum teres.— Angs. Hartm. Shand. FL, ed. 8, p. 417 

 (1861). Sphagnum squarroswn var. y teres, Schimper Torfm , p. 

 64(1858); Synop., p. 677 (1860). — Dioicous, in .small tufts or 

 intermixed with other species, soft, pale yellowish green, often 

 with a ferruginous tint. Stems slender, 4-8 inches high, pile 

 rufous red ; the cortical cells non-porose, in three strata, the 



