74 SUMMARY OF CURRENT RESEARCHES RELATING TO 



duction of hydrogen has hitherto only been observed in connection 

 with fermentation processes. He concludes that hydrogen carbonate 

 is directly reduced to formaldehyde by the chlorophyll apparatus in 

 presence of an adequate amount of light. 



L. Macchiati * claims to have established some new facts in support 

 of his contention that photosynthesis takes place in extracts prepared 

 from the green parts of plants, owing to the presence of a ferment. 

 Having powdered the leaves of five species of plants last autumn, and 

 stored the powder in dried sterilised flasks, he mixed these powders 

 with distilled water last March and succeeded in obtaining an evolution 

 of oxygen gas in varying quantities, when the temperature of the air 

 rose to 15° C. A triangular discussion as to the validity of his con- 

 tention is carried on between himself, G. Pollacci and A. Fiori in the 

 same periodical. 



Synthesis of Proteids.f — E. Laurent and E. Marchal arrive at the 

 following conclusions. Nitrogen in the form of ammonia is assimilated 

 both by normal and by etiolated chlorophyllous plants, the process 

 being more active in the former. Assimilation of nitrogen in the form 

 of nitrates by green plants is, with some exceptions, far more intense 

 in presence of light than in darkness. When nitrogen is assimilated in 

 darkness, the necessary energy is derived from the consumption of carbo- 

 hydrates. Whilst the "lower non-green plants can produce proteids in 

 absence of light, the synthesis in higher chlorophyllous plants can take 

 place only in the light. 



Deficiency of Nitrogen, Phosphoric Acid and Potassium in 

 Plant-Growth 4 — H. Wilfarth and G. Wimmer find that when nitrogen 

 or phosphoric acid is deficient, growth is more or less restricted, but the 

 composition of the dry matter is only affected when the deficiency is 

 very great. When the phosphoric acid is present in insufficient quantity, 

 the leaves become a dark green or bluish-green according to the amount 

 of nitrogen present, or in extreme cases the leaves blacken, beginning 

 from the edges. Very small amounts of potassium enable plants to 

 grow normally for weeks or months, but when the potassium is used up 

 photosynthesis ceases. Sugar-beet when grown with insufficient potas- 

 sium readily decays, and the sugar is often changed, partially or entirely, 

 into invert sugar. As in the case of the sugar-beet, the proportion of 

 leaves in potatoes is much increased when potassium is deficient, but 

 the yield and size of the tubers and the percentage of starch are reduced. 

 The effect of want of potassium on the appearance of the leaves and 

 plants is frequently very difficult to distinguish from that of fungi and 

 insects. 



Influence of Mineral Food on Sex in Dioecious Plants.§ — 

 E. Laurent has made a series of experiments, extending over seven years, 

 on the effect of the nature of the mineral food of a plant on the sex of 



* Bull. Soc. Bot. Ital., 1903, pp. 196-S. 



t Bull. Acad. Roy. Belg , 1903, pp. 55-114. See also Journ. Cliem. Soc, lxxxiv. 

 (1903) ii. p. 50G. 



X Journ. Landw., li. (1903) pp. 129-38. See also Journ. Cliera. Soc, lxxxiv. 

 (1903) ii. pp. 500-7. § Comptes Rendus. exxxvii. (1903) pp. 689-92. 



