758 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
becomes lacerated and the protoplasm becomes covered by a new one. 
"When tlie wall consists of several layers, these are stretched and 
lacerated in succession from without inwards. These facts support the 
hypothesis of apposition. 
Influence of Temperature on Caryokinesis.* — M. E. de Wildeman 
has experimentally investigated this subject, the objects of his experi- 
ments being the hairs on the filaments of Tradescantia virginica, Spiro- 
gyra , Cosmarium and Closterium. He finds that below a certain tempera- 
ture caryokinesis does not take place, at least in its entirety, while too 
high a temperature impedes this process and that of cell-division, 
and between the two there is an optimum temperature. For Trades- 
cantia this optimum was found to be about 45°-46° C., for Spirogyra 
12°, and for Cosmarium 24°. There are, however, also individual varia- 
tions. Light has no direct influence on this phenomenon ; the length 
of time required for nuclear and cellular division varies with the species 
and with the temperature. With Spirogyra and Cosmarium these pro- 
cesses are exceedingly slow at low temperatures ; with Tradescantia 
they can, of course, only be followed out through the summer months. 
C2) Other Cell-contents (including: Secretions). 
Chlorophyll-! — M. N. Monteverde has made a fresh series of 
experiments with the view of determining the number of distinct pig- 
ments present in an alcoholic extract of chlorophyll. 
If an alcoholic extract of leaves is treated with baryta water, and the 
precipitate extracted with alcohol, the solution has a yellow colour ; if 
this is again shaken with petroleum-ether after addition of a few drops 
of water, a separation takes place of the yellow pigments ; the petro- 
leum-ether containing carotin, identical with the carotin of the carrot, 
together with the green pigment ; the alcohol containing xanthophyll. 
The pigments contained in the petroleum- ether are termed by the author 
“ upper pigments,” those contained in the alcohol “ lower pigments.” 
By careful treatment the whole of the upper green pigment can be 
removed by alcohol from the petroleum-extract, leaving behind a golden 
yellow solution of carotin ; this green pigment does not crystallize. 
The alcoholic solution contains, in addition to xanthophyll, a “ a lower 
green pigment,” which crystallizes in tetrahedra, hexagons, or stars, but 
usually in irregular forms. The author believes that living leaves 
contain only the “ lower green pigment,” the upper one being a trans- 
formation-product resulting from the action of boiling water or of 
alcohol. 
Green and Etiolated Leaves.! — Herr W. Palladin has undertaken a 
series of observations with the view of determining the amount of albu- 
minoids in green and etiolated leaves of wheat and of Vicia Faba (with- 
out leaf-stalk). He finds the results point to the general conclusion that 
etiolated leaves may be divided into two groups according to the amount 
of albuminoids contained in them. In the case of stemless plants, 
* Ann. Soc. Beige Microscopie, xv. (1891) pp. 5-58 (4 pis.). 
f VIII. Congress Russ. Naturf. u. Aerzte (Bot.) 1890, pp. 32-7. See Bot. 
Centralbl., xlvii. (1891) p. 132. 
$ Ber. Deutscli. Bot. Gesell., ix. (1891) pp. 194-8. 
