818 SUMMARY OF CURRENT RESEARCHES RELATING TO 



heim's arguments, and agrees with his conclusion that the first 

 product of assimilation must be a substance containing less oxygen 

 than had previously been supposed. There is also a good deal in 

 favour of the view that this substance is Pringsheim's hypochlorin ; 

 but on the whole the author considers it more probable that it is a 

 product of decomposition of the colouring matter of the chlorophyll, 

 formed only on the addition of reagents. The statement of Prings- 

 heim that " in those cases where the chlorophyll-grains assume large 

 dimensions, as in bands, plates, &c.,,it is easily seen that the hypo- 

 chlorin does not appear everywhere where there is colour, but is 

 localized to certain spots," is not confirmed by Tschirch's observa- 

 tions. 



Function of Chlorophyll.* — Professor N. Pringsheim's latest 

 contribution to this subject is chiefly occupied with an historical 

 resume of our knowledge, and a reply to objections from various 

 sources to his previously published views, to which he adheres in all 

 essential points. Pringsheim does not agree with the view of some 

 other investigators f that the first product of assimilation is formic 

 aldehyde. This is not in accordance with the fact that in the light 

 the volume of oxygen evolved is equal to that of carbon dioxide de- 

 composed, taken into consideration in connection with the simultaneous 

 respiration of the plant. The total result can only be explained by 

 the product of assimilation being a compound which contains a smaller 

 proportion of oxygen than formic aldehyde. 



Vitality of the Chlorophyll-pigment.:}: — G. Kraus preserved fruits 

 of Cucurbita melanosperma in an ordinary sitting-room for more than 

 three years, at the end of which time mould began to appear on them. 

 The non-chlorophyllaceous cells were then found to contain proto- 

 plasm and other cell-contents apparently unchanged. In the chloro- 

 phyllaceons cells, on the other hand, the chlorophyll-grains were 

 transformed into green balls, having undergone a change similar to 

 that of the autumn colouring of the leaves of the horse-chestnut. The 

 colouring-matter of the chlorophyll appeared, however, to be entirely 

 unchanged. An alcoholic extract gave the typical spectrum of 

 chlorophyll with seven bands. 



Action of various Gases on Plants.§ — W. Detmer has experi- 

 mented on the influence of various gases on living plants. He found 

 the effect of nitrous oxide, hydrogen, and carbonic acid to be very 

 similar, hindering the further development of seeds and seedlings, and 

 preventing heliotropic curvatures and the greening in the light of 

 etiolated parts of plants. Chloroform also acted disadvantageously on 

 growth ; but respiration was not suspended in an atmosphere contain- 

 ing much chloroform. 



* Pringsheim's Jahrb. fur wiss. Bot., xiii. (1882) pp. 377-490. Cf. this Journal, 

 iii. (1880) pp. 117, 480 ; i. (1881) p. 479; ante, p. 220. 



t See this Journal, ante, pp. 361, 362, 526.' 



% Ber. Naturf. Ges. Halle, 1881, pp. 43-5. 



§ Landwirthsch. Jahrb., xi. (1882) p. 213. See Naturforscher, xv. (1882) 

 p. 272. 



