58 SUMMARY OF UUERENT RESEARCHES RELATING TO 



the general conclusion that the so-called unisexual forms have one sex 

 dominant, while the other is suppressed (i.e. in latent condition) ; but 

 there is a possibility that in certain stages and in certain plants, a single 

 sex may exist in a pure condition. Certain cases suggest that sex may 

 be pure in the gametophyte, while mixed in the sporopliyte. 



Physiology. 

 Nutrition and Growth. 



Development of Green Plant in Absence of Carbon Dioxide.^ 

 M. J, Lefevre * continues bis series of papers upon green plants grown 

 upon an amide soil in the absence of COo. The author, after remarking 

 upon the part played by amides as materials for reserve, construction, 

 food-material, and transport agents, proceeds to describe the apparatus 

 used in his experiments, also the preparation of culture-soils and the 

 choice of suitable plants. He thenjshows that valeric, butyric, propionic, 

 and uric fimides are unsuitable for these experiments, while the best 

 results are obtained from a mixture of tyrosin, glycocol, alanin, and 

 leucin, provided that the total amount of these substances does not 

 exceed l'i)-2 grm. per ;iO(> grni. of dry soil. 



M. Lefevre t also records the results of his ex])eriments upon plants 

 grown in absence of CO.,. He finds that only those plants can be used, 

 which are sufficiently vigorous and well-developed to adapt themselves 

 to the crisis due to experimental conditions. Where seeds have only a 

 small f Odd-reserve the seedlings can only be used after previous cultiva- 

 tion in the open air, while plants with a large food-reserve can be 

 experimented upon from the start of germination. Experiments show 

 that green plants, when sufficiently strong, will grow for several weeks 

 and even reach the fioweiing stage, if grown on an amide soil in absence 

 of CO2. The internal structure remains normal, but there is a slight 

 diminution in chlorophyll and in secondary formations, and a marked 

 increase in conjunctive parenchyma. That the amide compounds form 

 the source of the plant's supply of carbon, is proved by the fact that 

 control plants grown under similar conditions on ordinary soil, soon die. 

 It is also proved that CO^ in the soil is not utilised by green plants. 



In his concluding paper, the author | shows that the rapid increase 

 in the dry weight of plailts grown on an amide soil, without CO2, is not 

 the result of an osmotic upthrust of water, but is a real synthetic process ; 

 also that this synthesis is a chlorophyll function, impossible or much 

 reduced in the absence of light. In summing up, he concludes that 

 green plants have two sources of carbon (1) CO2 of the atmosphere, (2) 

 the carbon contained in the organic compounds of the soil ; he also puts 

 forward the hypothesis that chlorophyll has the power of synthesis, 

 independent of the normal process of assimilation. Finally, he shows 

 that the old idea of an impassable barrier between the nutrition of the 

 animal and vegetable kingdoms, must give place to the experimental, 

 biologic law, that organisms with chlorophyll, perform the work of 

 synthesis, while those without it, perform the work of analysis. 



* Rev. Gener. Bot., xviii. (1906) pp. 205-219 (1 fig.), 

 t Tom. cit., pp. 258-280 (4 figs.). % Tom. cit., pp. 302-310. 



