223 
Studies on Cyanophyceae. 
mucilaginous substance and to its rapid swelling under the action 
of the water.The contents represent the initial cell of the 
new filament.In the interior of the protoplasm, which is 
homogeneous throughout, no trace of a transverse division is to be 
distinguished up till now. The surrounding layer of mucilage 
-continuing to thicken, the initial element of the new thread is step 
by step liberated from the envelope of the spore ; then after 
becoming a little elongated, it divides in the transverse direction. 
The two new cells, thus formed, continue to divide indefiinitely in 
the same manner and always in the same direction (p. 255).” 
According to Borzi the endospore during germination thus becomes 
transformed into a delicate layer of mucilage, which envelopes the 
initial cells of the new thread (see also loc. cit. p. 254). I am 
however, rather inclined to imagine that the mucilage which causes 
the liberation of the spore-contents, is not (at least, not entirely) 
derived from the endospore, since both exospore and endospore are 
still recognisable in the spore-membrane after the contents are 
liberated (cf. Figs. 10 and 15). On p.257 (loc. cit.) Borzi describes 
the somewhat different germination of Nostoc lacustre ; here “ the 
initial cell of the young filament is divided a good deal before the 
membrane of the spore breaks open; in the interior of the spore 
the division of the cell into two new elements takes place. Soon 
after the envelope of the spore breaks on one side.and the two 
cells, becoming liberated appear enveloped by a thin sheath of 
transparent mucilage.” Borzi regards this method of germination, 
which differs from the other in the primary division taking place 
earlier, as normal in N. lacustre, which seems plausible. In one of 
the spores of fig. 8 on Plate VIII. a detached piece of the endospore 
is seen on one side, recalling one of the types of germination, I 
have described above; in the other figures however the detached 
piece is not figured. 
In his recent treatise on Cyanophyceae Brand devotes a 
section to the discussion of the gonidia ; these reproductive cells 
have long been known in the Chamaesiphoneae, where they are 
very well differentiated, and the older literature also contains a 
number of observations, pointing to their occurrence in other 
members of the blue-green Algae. Brand himself carefully describes 
their occurrence in Phormidium uncinatum , Gom., 1 where they 
arise singly by rejuvenescence of the whole or of the greater part 
of the cell-contents; exceptionally several gonidia (microgonidia) 
Brand. Morphol.-physiol. Betrachtungen, etc. Loc. cit. pp. 46 
and 47. 
1 
