514 SUMMARY OF CURRENT RESEARCHES RELATING TO 



vated with sugar or in symbiosis with vascular plants. Ammoniacal 

 nitrogen is assimilated by non-green lower plants (bacteria, moulds) 

 without the aid of light rays. In green plants the process can take 

 place in light or darkness, in green tissues and in those which have no 

 chlorophyll, but it is more active in the light. Nitric nitrogen can also 

 be assimilated in darkness by lower non-green organisms. In green 

 plants, with some exceptions (germinating seeds provided with reserve 

 material), the assimilation of nitrates is much more .intense in green 

 leaves exposed to the light, especially to the more refrangible rays. 

 When free nitrogen, or the nitrogen of ammonia or of nitric acid is 

 assimilated in darkness, there is consumption of hydrocarbonaceous 

 material which supplies the necessary energy for the work of reduction 

 of nitrates and of synthesis. The lower non-green plants can synthesise 

 proteids in the dark ; the necessary energy is supplied by organic com- 

 pounds. In green plants, especially the higher plants, this synthesis 

 takes place only in the light. Nevertheless, amides in limited quantity 

 may be produced in organs without chlorophyll (germinating seeds) in 

 the dark ; while a supply of certain amides (asparagin, glutamin) and 

 sugars may be followed by production of proteids in the dark. But in 

 the present state of our knowledge, it seems that the transformation of 

 nitric acid or of ammonia into proteids in an adult higher plant requires 

 the intervention of light. 



Assimilation in Green Plants.* — G. Pollacci describes the experi- 

 ments he has made to prove the existence of formic aldehyde in green 

 plants. He finds that this substance is formed in the green parts of 

 plants exposed to sunlight in the presence of carbon dioxide, and that 

 it can be distilled from the macerated leaves. It is not formed in 

 plants which have no chlorophyll (e.g. fungi), nor in green plants kept 

 in darkness, nor in the absence of carbon dioxide. He describes the 

 apparatus and reagents used and cites the writings of other workers at 

 this subject. 



The same author f replies to Czapek's criticism (in Bot. Zeit., 1900, 

 p. 153) of his work and claims priority for employing Schiff's reagent 

 (aqueous solution of fuchsin decolorised with sulphurous acid) for 

 experimenting on uninjured living green plants in light and darkness 

 and in the presence and absence of carbonic acid, and on plants which 

 contain no chlorophyll, and for demonstrating what was only surmised 

 previously — that formic aldehyde is a normal product of assimilation in 

 green plants. 



Use of Collodion for Detecting Transpiration. $ — L. Buscalioni 

 and Gr. Pollacci have discovered a new method of investigating the 

 transpiration of plants, by applying a solution of collodion to the sur- 

 face. The film sets hard and remains transparent on a dry surface, but 

 on a moist surface becomes opalescent, thus revealing with great 

 accuracy the points of escape of aqueous vapour from the transpiring 

 tissue. It is a great improvement on the older methods of applying 

 paper impregnated with chloride of palladium and iron or with cobalt 

 chloride, for the paper does not come into absolute contact with the 



* Atti d. Istit. Bot. Univ. Pavia, vii. (1902) pp. 1-21 (figs, in text), 

 t Tom. cit., pp. 101-3. J Tom. cit., pp. 83-95, 127-70 (3 pis.). 



