ON A MINUTE NOSTOC WITH SPORES, ETC. 367 



On a Minute Nostoc with Spores, ivith Brief Notice of 



RECENTLY PUBLISHED OBSERVATIONS On COLLEMA, &C. 



By William Archer. 



The appearance of a highly interesting and noteworthy 

 communication from Professor Max Reess, conveying a de- 

 scription of certain novel experiments instituted by him on 

 the growth of a Collema from the spores, and giving his 

 views as to the bearing thereof as regards Nostoc,^ Avhich I 

 have only just seen, recalls to my recollection a seemingly 

 remarkable though isolated example of a not vmcommon 

 minute aquatic Nostoc, with spores, brought forward by me 

 at a recent meeting of our Microscopical Club, but not 

 publicly exhibited, from want of time, and since then some- 

 how overlooked to be recorded. 



The little Nostoc, presenting the speciality to which I am 

 desirous of directing attention, is a very minute one, though 

 the dimensions of the subglobose or elliptic fronds vary 

 much. It is rather common in moor and certain bog pools. 

 On account of its small size, therefore readily caj^able of 

 compression, and its pellucid character, the elegant arrange- 

 ment of its tortuously twisted rather large moniliform fila- 

 ments, is often nicely seen, and this causes it to be a very 

 pretty and favorable illustrative example of its type for ex- 

 amination in its entirety under the higher powers of the 

 microscope. Its minute size calls to mind Nostoc minimum 

 (Currey),^ but in it the cells are described as quadrate, with 

 a sinus at each side, lending a crenate outline to the fila- 

 ments, and the heterocysts are large, whilst here the cells 

 are orbicular, or for a time slightly flattened at the junctions, 

 and the heterocysts are but slightly wider, though longer 

 than the ordinary cells. This plant is probably identical 

 with Nostoc paludosum (Ktltz.), though, as regards anything 

 to be deduced from the heterocysts, Kiitzing is silent. But 

 the interesting point connected with it is a single example of 

 it having presented indubitable "spores," of precisely similar 

 nature to those in Sphserozyga, &c., but with the peculiarity 

 of their being always placed singly between two heterocysts. 

 The pairs of heterocysts with the intervening spore occurred 

 at just about the same intervals as in ordinary examples 



* Professor Max Reess, " Ueber die Enstebung der Flechte Collema 

 glaticescens, Hoffm., durcli Aussaat der Sporen derselbea auf Nostec 

 lichenoides, Vaucli." In ' Monatsb. der k. Akad. der Wiss. zu Berliu,' 

 Oct., 1871, p. 523. 



^ Currey " On Freshwater Algae," in ' Quart. Journ. of Micr, Sci.,' vol. 

 vi (1st ser.), page 216. 



