Physiologie. 109 



foggy da3's, but on Standing for some days the extract no longer 

 gave the aldehyde reaction; on exposing films of such aldehyde- 

 free Chlorophyll to sunlight in ihe presence of moist carbon dioxide, 

 the forma Idehy de reaction reappeared. Even in the absence of 

 carbon dioxide slight traces of aldehyde were found after exposure 

 to sunlight (it is suggested that in this case carbon dioxide may be 

 formed by photochemical decomposition of some constituent of Chlo- 

 rophyll); in the dark formaldehyde is never produced. The results 

 indicate that formaldehyde, as it is produced in plants, enters into 

 somewhat stable combination vvith a constituent of Chlorophyll. 

 Such a meihylene derivative will in presence of water undergo 

 only slight hydrolysis, and equilibrium will be maintained in the 

 presence of only a very small amount of free formaldehyde; as 

 this is removed (by polymerisation or otherwise) the Chlorophyll 

 methylene derivative will undergo further hydrolysis with the 

 setting-free of further small amounts of aldehyde, hence the latter 

 never accumulates in harmful quantity. F. Cavers. 



Thoday, D., Experimental researches on vegetable assi- 

 milation and resp;ration. VI. Some experiments on 

 assimilation in the open air. (Proc. Roy. Soc. LXXXII. 



• p. 421—450. 1910.) 



In the experiments described, the half-leaf dry-weight method 

 of Sachs was employed, with modifications for avoiding errors due 

 to shrinkage of the insolated half-leaves. Turgid leaves of Helianthus 

 annuus were found in bright sunlight to increase in dry weight 

 17 mg. per hour per sq. decim., hence the high value given by 

 Sachs is confirmed; even a slight loss of turgor, however, was 

 accompanied by a diminution in the rate of increase in dry weight. 

 It is suggested that the low results of Brown and Escombe in 

 bright diffuse light indicate that the stomata of Helianthus leaves 

 open to their füll extent only in light which is similar in quality 

 to sunlight and which approaches it in intensity. Detached leaves 

 of Catalpa bignonioides when fully turgid increased 5—6 mg. per 

 hour per sq. decim. in bright sunlight; here the stomata occur only 

 on the lower side of the leaf. The author considers the effect of 

 detachment from the plant upon the rate of assimilation, and gives 

 evidence in support of Sachs's assumption that concurrently with 

 assimilation part of the products of photosynthesis are translocated 

 from leaves still attached to the plant. F. Cavers. 



Vlnes, S. H., The proteases of plants. VII. (Ann. Bot. XXIV. 

 p. 213-222. 1910.) 



The author has continued his work on the proteolytic enzymes 

 of plants, and finds that both malt extract and taka diastase con- 

 tain enzymes capable of digesting fibrin and of Splitting peptone; 

 from the malf extract he isolated the peptone-splitting enzyme free 

 from the fibrin-digesting body, and from the taka diastase he sepa- 

 rated each from the other. Both enzymes act best in acid media. 

 By special methods of preparation. however, the author obtained a 

 Protease ffibrin-digesting enzyme) which acted best in neutral and 

 basic media; hence he has obtained from plants two distinct pro- 

 teases corresponding respectively with «-protease (weak and acting 



