254 BOTANICAL GAZETTE | MARCH 
Texas, and Chico, California. At each of these places between 600 and-1500 
varieties of Opuntia were under cultivation. The general purpose of the inves- 
tigations was economic, but incidentally the behavior of these plants was very 
suggestive. Spiny plants grown near the coast of Texas mature spines much 
more slowly than in drier regions. Changes in the environment seem to have 
more effect on the production of spicules (bristles) than of spines, the evidence 
indicating that conditions unfavorable to vegetative production stimulate the 
growth of spicules. An interesting contrast between the conditions in Southern 
Texas and California is shown by the fact that the former region is favorable 
for the production of vegetative growth, while California is better adapted to 
fruit production. It was found that many species are not promising for breed- 
ing purposes because of lack of variability; they are very constantly spiny, 
and spine protection seems to be directly proportional to plant vigor. The 
power of recovery from the effect of low temperature is rémarkable, especially 
when the succulency of the plant is considered. very interesting observa- 
tion was that in many of the species, especially the larger ones, the plants 
grown from cuttings and those grown from seeds are very different in appear- 
ance; the latter are tree-like and the former are headed on the ground without 
distinct stems.—J. M. C. 
Mitosis in Conjugatae:—In agreement with the earlier work of LUTMAN, 
VAN WISSELINGH” finds that the nuclei of Closterium show at all stages an 
essential correspondence with those of higher plants. Division is strictly 
mitotic, and the chromosomes, more than 60 in number and of various lengths, 
all come directly from the reticulum, which is composed of but one material. 
They are not placed in a ring around a central spindle at metaphase, as LAUTER- 
BORN thought, but form a uniform plate of the usual type. VAN WISSELINGH 
denies the presence of a continuous spirem at prophase and telophase 4s 
reported by Lurman. The nucleolus is not of the peculiar kind previously 
described for Spirogyra; in C. Ehrenbergii it is really an agglomeration of many 
small nucleoli. No centrosomes were foun 
In Eunotia,® also, the nucleus divides mitotically, as in other diatoms, but 
well developed chromosomes are not formed. The nuclear reticulum gives 
rise to small irregular bodies which become arranged in the form of a “nuclear 
plate” around the characteristic “central spindle” of the diatoms. The nuclear 
plate divides to form two daughter plates. VAN WISSELINGH’s results here 
agree with those of KLEBAHN and KarsTeEN on other diatoms, but not with 
those of LAUTERBORN, who found in several species long and well developed 
chromosomes in both mother and daughter nuclei. 
2 Van WisseLincu, C., Uber die Kernstruktur und Kernteilung bei n=. 
Siebenter Beitrag zur Kenntnis der Karyokinese. Beih. Bot. Centralbl. 29*:499-43* 
pl. 10. 1913. 
VAN WISSELINGH, C., Die Kernteilung bei Eunotia major Rabenh. Achter 
Beitrag zur Kenntnis der Karyokinese. Flora 105: 265-274. pl. 10. 1913- 
