414 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(4) Chemical Chang'es (including- Bespiratiou and Fermentation). 



Formation of Starch from Organic Solutions.* — M. ii. Laurent finds, 

 as the general result of a series of experiments, that, in the potato, the 

 following substances can be transformed into starch, viz, : — glycerin, 

 dextrose, levulose, galactose, saccharose, lactose, and maltose, all of them 

 except the first being sucroses. The following substances appear to have 

 no efiiect as producers of starch, viz. : — monatomic alcohols, glucol, 

 tetratomic and hexatomic alcohols, ethers, aldehydes, fatty bodies, amines, 

 amides, aromatic compounds, glucosides, and alkaloids. 



It must not, however, be assumed that no body which cannot be con- 

 verted into starch is useful for the nutrition of chlorophyllous plants. 

 Such a substance may serve neither to aid in growth in length, nor in 

 the formation of reserve food-materials, but for use in respiration, A 

 typical instance of this distinction is furnished in Aspergillus niger. 

 While saccharose and glucose are sufficient for the full growth of this 

 fungus, alcohol, acetic acid, and even oxalic acid, are burnt by the 

 mature plant. While these substances do not serve directly for nutri- 

 tion, they yet, by their combustion, develope sufficient energy to assist 

 in the supply of nutriment to organs already formed. 



Development of Nitrogen in Putrefaetion.| — Herr B. Tacke finds, 

 as the result of a series of experiments, that the ordinary view that free 

 nitrogen can result from the decomposition of vegetable substances only 

 when free oxygen is excluded, is incorrect. Free nitrogen is not formed, 

 whether free oxygen be present or not, if the decaying substances do not 

 contain nitrates. But, if the substance contain a nitrate, then in the 

 presence or absence of free oxygen, the nitric acid is reduced either to 

 the state of free nitrogen or to that of one of the intermediate oxides of 

 nitrogen, NgO, NO, or N2O3. The ordinary gaseous products of the 

 decomposition of vegetable substances are, according to circumstances, 

 carbon dioxide, hydrogen or sulphuretted hydrogen, and marsh gas. 

 The microbes by whose agency the reduction of the nitrates is effected 

 do not bring about any elimination of free hydrogen. 



y. General. 



Epiphytic Vegetation of the Tropics.J — Continuing his investiga- 

 tions on tropical plants, Herr A. F. W. Schimper enumerates the species 

 of epiphytic Phanerogams and Vascular Cryptogams in Tropical and 

 Southern America, 119 belonging to the Orchidacese. The mode of 

 adaptation of the seed for the epiphytic habit is threefold : in most 

 cases they have a succulent envelope which is devoured by animals, 

 and the seeds themselves are then voided on to the branches of 

 trees ; or they are so small as to be carried readily by the wind to 

 fissures in the bark (Orchidacege) ; or they are provided with a floating 

 apparatus. As respects their nutrition ; they either find their nutriment 

 on the moist surface of the host, and are then usually protected against 

 desiccation by the presence of receptacles for holding water ; or tliey 



* Bull. Soc. E. Bot. Belg., xxvi., part 1, 1887 (1889) pp. 243-70, Cf. this 

 Journal, 1886, p. 643. 



t Landwirth. Jalub., xvi. pp. 917--39. See Bot. Centralbl., xxxvii. (1889) p. 56. 



t Bot. Mitth. aus d. Tropen, Heft 2, 162 pp. and 6 pis., Jena, 1888. i^ee Bot. 

 Centralbl., xxxvii. (1889) p. 180. Cf. this Journal, 1888, p. 772. 



