SUMMARY OF CURRENT RESEARCHES RELATING TO 
77 
*2 
Heliotropic Sundew.* — Prof. B. D. Halsted states tliat tlie giant 
American sundew, Drosera filiformis, is heliotropic ; a new flower opens 
each day at the top of the bend of the curved inflorescence ; and this 
flower, when it opens, invariably faces the morning sun. 
(4) Chemical Changes (including Respiration and Fermentation). 
Influence of Light on Respiration. f — M. K. Purjewicz has made an 
extended series of observations on this subject. His general results 
agree with those of Bonnier and Mangin J that light has a prejudicial 
effect on respiration in plants. The mode of estimating the amount of 
carbon dioxide produced was by precipitation with baryta water. The 
object examined was exposed alternately to light and darkness for periods 
varying between J and 1J hours. 
With hymenomycetous fungi this result was obtained in 42 experi- 
ments out of 43, the reduction in the amount of C0 2 produced in a 
given time varying between the proportions of 0*58:1 and 0*90:1. 
The period of growth taken was either before the separation of the 
margin of the pileus from the stipe or at the maturity of the pileus ; 
at which periods the intensity of respiration is very constant, while in 
the intermediate period of rapid growth it varies rapidly. Experi- 
ments with roots and rhizomes of Flowering Plants, with flowers, and 
with etiolated leaves, gave no uniform result, the intensity of the 
respiration being in some cases increased, in others decreased, by the 
action of light. 
Formation and Decomposition of Oxalic Acid and its Function in 
the Metabolism of Fungi. § — From a very extended series of observa- 
tions on certain fungi, belonging chiefly to the Mucor , Aspergillus , and 
Penicillium group, Herr C. Wehmer dissents from the views entertained 
by other authorities with regard to the importance of oxalates in the vital 
economy of the plant. Oxalic acid he regards as a secondary, but not 
always a final, product of metabolism, which may sometimes be excreted, 
or the formation of which may sometimes be altogether suspended. 
The conclusions were the result of the culture of the fungi in a great 
number of different nutrient solutions. The author believes that the 
same laws regulate the formation of oxalates in the higher plants as in 
fungi, and that their production is dependent entirely on the conditions 
in which their growth takes place ; even the entire absence of oxalic 
acid, or of its salts, has no special significance as regards the vital 
economy of the plant. 
As regards the conditions most favourable for the formation of oxalic 
acid, || Herr Wehmer finds, in the case of Aspergillus niger , an optimum 
temperature (34°-35° C.), above which an increase of temperature is 
decidedly unfavourable to the formation of free oxalic acid. Light has 
a powerful effect in bringing about the decomposition of oxalic acid ; 
* Bull. Torrey Bot. Club, xviii. (1891) pp. 212-3. 
t Schrift. Naturf.-Gesell. Kiew, xi. (1890) pp. 211-59. See Bot. Centralbl., xlvii. 
(1891) p. 130. I Cf. this Journal, 1886, p. 1016. 
§ Bot. Ztg., xlix. (1891) pp. 233-46, 249-57, 290-8, 321-32, 338-46, 354-63, 
370-4, 385-96, 401-7, 417-27, 433-42, 449-55, 465-78, 511-18, 531-9, 547-54,563-71, 
570-84, 596-602, 611-20, 630-8. 
|| Ber. Deutsch. Bot. Gesell., ix. (1891) pp. 103-83, 218-28. 
