82 SUMMARY OF CURRENT RESEARCHES RELATING TO 



capable of general application. Two types of endotropic mycorhiza 

 may be distinguished ; one adapted for the fixation of nitrogen ; the 

 second for the absorption and modification — perhaps the oxidation — of 

 the products of the soil before liberation in the tissues of the higher 

 plants. 



Absorption of Nitrogen by Leguminosse.* — Herr J. Lutowslawski 

 finds that, in the case of peas and lupins, an increase in the amount of 

 nitrogen commences with the beginning of the independent growth of 

 the plant, i.e. soon after the close of the period of germination ; in 

 all cases before the commencement of the formation of the inflorescence. 

 It attains its maximum after flowering, when the pods begin to be formed, 

 after which it gradually decreases. The period, therefore, for using 

 these crops as manure, to increase the fertility of the soil, is at the com- 

 mencement of the formation of the fruit. 



Function of Sodium. f — According to Herr M. Stahl-Schroder, 

 sodium is taken up largely by plants, in the presence of plenty of 

 potassium, only when in combination with some acid of which the plant 

 requires considerable amounts, such as phosphoric or nitric. The 

 sodium remains mainly in the lower parts of the plant. Sodium cannot 

 replace the potassium necessary for the production of the organic matter 

 of plants. 



Absorption of Iodine by Plants. X — From a series of experiments 

 carried on by'M. P. Bourcet, the result is attained flat different plants 

 vary greatly in their power of absorbing iodine from a soil containing 

 a given quantity of that element ; some species refusing it altogether. 

 A difference in this respect is exhibited even between different species 

 of the same genus; but some orders appear to possess the property in a 

 greater degree than others ; as, e.g., the Liliaceae and Chenopodiacese 

 more than the Solanaceae or Umbelliferae. 



Indirect Action .of Light on the Stem and Leaves.§ — From a com- 

 parison of plants grown (1) completely exposed to light ; (2) completely 

 in the dark ; (3) so that the lower leafy part of the stem is in the light, 

 -while the terminal bud is in the dark ; M. E. C. Teodoresco draws the 

 following general conclusions. In the third case (with the exception 

 of twining and climbing plants) the leaves are larger than in the second 

 case, the difference being in some instances (Helianthus tuberosus) as 

 much as 50 to one. The thickness of the leaves and that of the palisade- 

 parenchyme may be one and a half times as great in plants partially 

 illuminated as in those grown entirely in the dark ; the walls of the 

 epidermal cells are wavy in the former case, but not in the latter. In 

 the stem the contrast is still greater. In a plant partially illumi- 

 nated, the conducting tissue and the lignification of the walls of 

 the mechanical tissue, approach more nearly in their development to 

 those in a plant grown entirely in the dark. In a plant entirely deprived 

 of light, starch is altogether wanting in the tissues of the stem ; while in 



* 'Beitr. z. Lebre v. d. Stickstoffernabrung d. Leguminosen,' Halle a. S., 1898, 

 32 pp. See Beiheft z. Bot. Centralbl., ix. (1899) p. 72. 



t Jahrb. Lundwirtb., xlvii. pp. 49-84. See Journ. Chem. Soc, 1899, Abstr. ii. 

 p. 789. X Comptes Rendus, exxix. (1899) pp. 768 70. 



§ Rev. Gen. de Bot. (Bonnier), xi. (1899) pp. o69-97, 430-5 (1 pi. and 12 figs.). 



