82 Dr. F. Cohn on the Development and Propagation 



SijihteropJcn anmilina, Ag., is one of the rarer freshwater Alga;, 

 which is not observed, Hke most of these phuits, every wliere and 

 at all seasons, but only at long intervals and under peculiar cir- 

 cumstances ; it consists, like all the Conferva^, of cells of variable 

 length, connected in a single row into long lilaments, and is 

 characterized by a peculiar arrangement of the chlorophyll. 

 Ehrenberg has already remarked that it covers extensive surfaces 

 about Berlin with a red coating, and hence may have given rise 

 to traditions of "blood-rain." Near Bremen, where it was dis- 

 covered by Treviranus, it occurs upon flooded tracts. At Breslau 

 I found it the first time at the end of October, last year, in 

 a potato-field wliich had been laid under water by the great 

 overtlow of the Oder in the last week of August. The Spharoplca 

 covered the field, whicii had dried again after the retreat of the 

 water, as an almost uninterrupted felt, of a beautiful red-lead or 

 vermilion colour on the smooth upper surface, and green on the 

 under side, where it was disentangled nito the separated filaments. 

 The red colour dej)ended upon the sjiores with which the fila- 

 ments of the Spluoruplca were completely filled uj) ; oidy those 

 filaments which were exposed to light and air on the surface of 

 the felt fructified ; the under side, resting on tiie ground, con- 

 tained only vegetative filaments of the normal green colour. 



The structure of the Sph(Troplea-s\>oves is very simple; they 

 are red globules, usually from 1-125 to 1-100'" in diameter, 

 surrounded by two hyaline membranes, of which the inner lies 

 close upon the contents, while the outer is somewhat separated 

 and is elegantly creased. The spores of Sphan'ojdea are usually 

 described as stellate; Kiitzing however states that they arc 

 encircled by spiral bands. Both these assertions are justified to' 

 a certain extent : it depends upon the position of the spores 

 whether they look like many-rayed stars, or as longitudinally 

 streaked, smooth-bordered globes. The outer coat of the spore 

 is so folded that the folds meet at the two poles of the globe like 

 80 many meridians. Hence if we look at the pole of a spore, 

 the folds are seen surrounding the globe like a frill, in a sharp- 

 angled zigzag; while if we look upon the equator of the spore 

 with the axis parallel to the object-glass, the folds may be traced 

 in their whole course as longitudinal lines. In many spores, 

 especially the large ones, the ])laiting of the outer coat is very 

 irregular, and forms merely wart-like elevations without any 

 definite arrangement. Sulphuric acid causes an expansion of 

 this coat, but does not destroy it ; iodine and sulphuric acid colour 

 it bright yellow. 



The contents of the spores consist of rather large starch-gra- 

 nules, and protoplasm which is coloured bright vermilion-red by 

 a peculiar colouring matter ; they contain a red oil which stands 



