1922] CURRENT LITERATURE 331 
effective in securing an exact distribution of the chromatin. The author pro- 
poses for it the special term ‘“‘syndinial mitosis,’’ and expresses the opinion 
that further study of the free peridines will show that nuclear division in such 
forms is also of this type-—G. W. MarrTIN. 
Cytology of Porphyra.—Since a cytological study of the Bangiales might 
throw light upon the much discussed but little investigated problem as to 
whether this group is primitive or reduced, whether it should stand at the 
beginning or at the end of the red algae, IsHrKAwaA3 fixed material and has 
described several critical stages in the life history of Porphyra tenera, a charac- 
teristic genus of the order. 
e cell wall shows no cellulose reaction, but responds to tests for pectic 
substances. The large stellate chromatophore contains one conspicuous 
pyrenoid which has often been mistaken for a nucleus, the real nucleus (only 
1.5-2 win diameter) being hard to detect in living material, although easy to 
see in well stained preparations, where it appears as a black globule with no 
structural differentiation. At division the nucleus elongates, and splits by 
longitudinal fissures into three filaments which constrict in the middle, so 
that three pieces go to each pole. The process looks like that described for 
some Cyanophyceae, especially Synecocystis. The figures show neither nucle- 
olus nor nuclear membrane, so that the type appears to be very primitive. 
The antheridium consists of 64 or 128 cells, and the spermatium has a 
chromatophore and a group of three chromosomes without any nuclear 
membrane. ‘The earpogonium is slightly prominent at both ends, the 
prominence constituting a rudimentary trichogyne. Spermatia were found 
attached to the trichogyne, but the actual process of fertilization was not 
observed, nor was there any study of the first and second divisions of the 
zygote. It seems reasonable, however, to suppose that reduction of chromo- 
somes occurs during these divisions, as in many other algae. 
’ ISHIKAWA would regard Bangiales as a connecting link between the 
Cyanophyceae and the Florideae, a conclusion which is helped by the fact that 
Porphyridium, a genus sometimes placed in one group and sometimes in ae 
other, has no sexual reproduction. So far as pigments are concerned, so 
of the Rhodophyceae have phycocyan and some of the Cyanophyceae oe 
phycoerythrin. 
Although a careful investigation of the whole life history of several members 
of the Bangiales is desirable, it seems probable that any future study of the 
group will confirm IsHtkawa’s conclusions.—C. J. CHAMBERLAIN. 
Ecology of Urtica dioica.—In an interesting study of the factors which 
locally limit the distribution of the common nettle, Urtica dioica, OLSEN‘ 
35: 206-218. 
* OLsEN, CarsTEN, The ecology of Urtica dioica. Jour. Ecol. 9:1~-18. pl. 1. 1921. 
3 Isutkawa, M., Cytological studies on Porphyra tenera. Bot. Magazine Tokyo 
1921. 
