ie 
d 
1899] CURRENT LITERATURE 227 
Blackman was not able to confirm Dixon’s observations on the number of , 
chromosomes. Dixon reported eight chromosomes in the nuclei of young 
embryo-sacs, eight in the nucleus of the oosphere, usually twelve but some- 
times eight or twenty-four in the nuclei of the cells sheathing the oosphere. 
Dixon was not able to make a direct count of the chromosomes in the’ 
more extensive, shows the number of chromosomes in the various nuclei to 
be as follows: In the egg, twelve; in pollen mother cells, twelve; nuclei of 
the female gametophyte, twelve; first division after fertilization, twenty-four ; 
later divisions, Over twenty-one and presumably twenty-four. 
On account of recent work on Gingko, Cycas, and Zamia, a careful search 
“astmade for traces of cilia, blepharoplasts and centrosomes, but no such 
‘uctures could be found, and the evidence furnished by Pinus was believed 
to bear out the Conclusions of the various writers of the Bonn school against 
a, Presence of centrospheres in plants higher than mosses. — CHARLES J. 
CHAMBERLAIN, 
POFESOn W.F. Ganonc has published in the Annals of Botany (12 : 423- 
*74: 1898) further results of his investigation of the Cactacez, giving an 
group is © comparative morphology of the embryos and seedlings. The 
logeny oo and so Plastic that the author anticipates that the phy- 
pletenesg * Senera and species may be discovered with remarkable com- 
a . . 
ee ao} the humerous germination experiments, some interesting 
} ¢ . . . 
na ee reached. Beginning with Pereskia, and passing by way of 
Cereus an 
of the germinated embryos, and consequent 
Surface brought about by the increasing approach to a spher- 
ypocotyl and diminution of the cotyledons. This pro- 
~abeeaes embryos runs parallel with the condensation in 
s behind it, so that adult and embryo do not always cor- 
adaptive chan Pianation suggested is that as the adult acquires a certain 
Work back into egy ie becomes more fixed and intensified, it tends . 
dividuals, until j ‘rand earlier stages in the ontogeny of the successi 
© 8enera is constructed, based upon these recent observa- 
Previously recorded facts. Neglecting the numerous 
f second represented in our flora, and which for the most part 
ae as follows - > 'mportance, the main points of the proposed sree 
family, aa th Sreskia is regarded as nearest to the original stem-form oO 
© earliest derived line was Opuntia. From the primitive 
“Which are not 
