1grr] BROW N—LACHNEA SCUTELLATA 207 
region around the centrosome, but it may begin at any point. 
After the wall has become thickened, it is easy to determine that 
it is a distinct wall, with plasma membranes on both sides of it. 
This is shown especially clearly in material which has been shrunken, 
when it is possible to find, side by side, cases in which all of the 
contents have a normal position, and others in which either the 
plasma membrane around the spore or the one lining the epiplasm 
is drawn away from the wall. At this stage the astral rays are 
still plainly visible. 
The stage at which the nucleus retracts its beak and rounds 
up is somewhat variable, but it usually does not take place until 
after the formation of the wall. When the beak is withdrawn, the 
centrosome may be left in the cytoplasm, but more frequently it 
remains in contact with the nuclear membrane. In either case it 
finally disappears. 
As the spore reaches its mature size the wall around it thickens 
and becomes the exospore. 
Discussion 
HETEROTYPIC MITOSIS 
The method of reduction in the number of chromosomes in 
Lachnea is quite similar to that described in Dictyota (WILLIAMS 
37), Fucus (YaMANOUCHI 41), and in a large number of the higher 
plants. The chromosomes are arranged end to end in the prophase 
of the heterotypic division, and there is no evidence of a parallel 
fusion of spiremes. 
The reducing divisions in Lachnea are quite unlike those in 
Phyllactinia (HARPER 23). This is perhaps not surprising in view 
of the great dissimilarity which, according to the work of Davis 
(12), YaMANoucut (39), and Lewis (25), is shown by different 
genera of the Rhodophyceae. The great difference between the 
mitoses in Lachnea and Phyllactinia would certainly make it unsafe 
to carry any conclusions in regard to nuclear phenomena from one 
form to the other. 
There is in Lachnea nothing resembling the double reduction 
described in some other Pezizineae by FRASER (14), FRASER and 
