ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 83 



genera and species this curvature is more or less strengthened by the 

 capacity for swelling of the masses of cellulose in the ligneous layer 

 increasing more or less from the outside inwards. 



Aerial Vegetative Organs of Orchidese in relation to their 

 Habitat and Climate.* — An examination of the structure of a large 

 number of both native and tropical Orchidese leads P. Kriiger to the 

 following general conclusions on this subject: — Starting from the 

 native species, there may be seen, both in the foliar and axial organs, 

 a series of gradual variations, which increase in importance as the 

 climatic conditions of the species vary from ours. In one group of 

 tropical orchids the original herbaceous habit is still maintained ; 

 while contrivances to suit other conditions are perfected in changes in 

 the parenchyma, having for their purpose the absorption of the water 

 necessary for the j)lant, and protection from transpiration. In a 

 further stage the herbaceous form is abandoned as unsuitable, and 

 the succulent form assumed ; while in a third type the development 

 of a mechanically firm and resistant system strengthens the epidermal 

 tissue, or assists in the formation of special receptacles for water, or a 

 combination of the two means. All these changes are accompanied 

 by corresponding changes in the cuticle, having for their object the 

 diminution of transpiration in tropical orchids. 



Assimilation of Carbonic Acid by Protoplasm which does not 

 contain Chlorophyll.t — By experiments on PeniciUium glaucum, 

 J. Eeinke finds that all the carbon-acids tested, with the exception 

 of carbonic, formic, and oxalic acids, are of equal value for its 

 nutrition, but are useful only when in combination with bases. The 

 methyl-group can in many cases supply the fungus with carbon ; as 

 also can the group Cg Hg, Before it becomes serviceable to the plant, 

 the carbon of the acids must apparently enter into combination with 

 hydrogen, in consequence of a process of reduction brought about by 

 the assistance of water, and by means of protoplasm. 



Artificial Influences on Internal Causes of Growth.^ — B. WoUny 

 points out that the reason why the secondary shoots of woody plants 

 grow more rapidly when the main stem is decapitated, is not merely 

 that they receive a better supply of nourishment, but that the con- 

 ditions of the soil are altered through greater access of moisture 

 and warmth. The popular idea that vegetation keeps the ground 

 moist is exactly the reverse of the truth. 



Absorption of Food by the Leaves of Drosera.§— By a series of 

 experiments, M, Biisgen has confirmed in a very striking manner 

 the observations of Kees and Darwin as to the capacity of Drosera 

 rotundifolia for absorbing nutriment through the leaf. The number 

 of inflorescences and capsules was found to average very much higher 

 (from three to five times as many), when the leaves were fed with 



* Flora, Ixvi. (1883) pp. 435-43, 451-9, 467-77, 499-510, 515-24 (2 pis.), 

 t Keinke's Unters. Lab. Gottingen, Heft 3. See Bot. Ztg., xli. (1883) p. 551. 

 X Wollny's Forsch. Geb. Agrikulturpliysik, vi. (1883) pp. 97-134. See Biol. 

 Centralbl., ill. (1883) p. 385. 



§ Bot. Ztg., xli. (1883) pp. 569-77, 585-94. 



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