52 THE ALGA-FLORA OF CAMBRIDGESHIRE. 
of this family are probably mere stiidikionin of aociomone “a 
higher forms’? Or for Itzigsohn’s statement }+—* I have observed 
these dimorphose Chroococcus cells associated with species of Toly- 
rte and believe that all the forms described as ——_ are 
nothing more or less than spores of Nostocer’”’? I have studied 
of the year and under a great variety of conditions of humidity, 
light, and temperature, and the answer I unhesitatingly give is— 
No: certainly not. Nor is it for me to comment here on the 
— with which most of Wolle’s observations were made, 
g been done elsewhere,t but rather to indicate the 
difficu ities mitieh beset the investigator of this problem. The 
reproduction of the Nostoce cytonemace ans of 
mogones is a fact which can be studied and confirmed even by 
the most casual oe e presence of anos other than 
a very difficult saallae ‘to demonstrate. heals spores may be in 
some cases ‘“ Chroococcus-like forms,’ but a critical examination 
will, as a rule, readily discriminate between the stages of ~“ 7 
plants and the Chroococcaceous alge with which the inter- 
mingled. The difficulties in attempting to follow out the Vfe-histories 
= these alge are not merely due to the confused intermingling of 
arious stages of plants belonging to many different genera, but 
ans to the fact dint these plants, if isolated for cultivation from the 
polymorphic matrix in which they occur, will, if they develop at all, 
often do so in an unnatural manner. This being so, may not nite 
in reality include stages of Saas sae of more than one species, 
or even more than one gen However, be that as it may, when 
we find a plate of the very pa i drawings, including many genera 
a confusion similar t in which they naturally occur, and @ 
ticket * se side —— ae they are all forms of one plant," is it 
to be accepted withou call for more evidence concerning the 
se tendneties of pion hs of plant-life ? 
* Freshwater pe of the United shy 324, 
+ Cfr. . a translation of a passage in Itzigsohn’s Shizzen zu 
einer Lebensgeschichte ‘is ’ Rapetelpion resus 1853. 
est, ‘N. Amer. Desm.,’ Trans. Linn. Soe. bot. 2 ser. v. 229. 
§ Hansgirg in Oesterreich. Bot. Zeitschr. 1884, xxxiv. 393; West in Journ. 
a Soc. bot. xxx. 272, pl. xv. f. 23-38; West & G. S. West in Journ. Bot. 
{| me Plecteneae peculiar rounded thick-walled cells of a yellowish colour 
are sometimes me et with at or near the bases of the branches. 
“| Wolle, J. c. pl. clxxxiy. and pl. exci. 
