994 SUMMARY OF CURRENT RESEARCHES RELATING TO 



place at the same time, and their relative intensity determines whether the 

 growth of the plant is accelerated, retarded, or remains the same. With 

 more sensitive plants (Ipomsea purpurea, Linum usitatissimum, Trcpseolum 

 majus) the retardation is the stronger force ; in those which are less sensitive 

 (Helianthus annuus, Gucumis sativus, Fagopyrum esculentum) the retardation 

 is perceptible to measurement only during the first days, when the weight 

 is not nearly sufiicient to rupture the tissues. With greater weight it can- 

 not be measured even on the first day, although no doubt present. But 

 while with more sensitive plants the retar(lation is permanent, with the less 

 sensitive it disappears altogether, and after the first day a distinct accelera- 

 tion is perceptible. Differences are also dependent on the amount of weight 

 and the age of the plant. The growth of the plant in thickness is not 

 reduced. 



Reproduction of parts of Plants.* — Prof. F. W. C. Areschoug explains 

 the tendency of some parts of plants to produce leaf-buds, and others roots, 

 or of the same part to produce buds or roots under different conditions, by 

 the hypothesis that buds are produced by those parts where there is a larger, 

 roots by those parts where there is a smaller, accumulation of nutrient 

 material ; stems requiring a larger amount of nutriment than roots, in con- 

 sequence of their larger size and greater complexity of structure. Thus in 

 all trees the strongest shoots spring, not from the lower, but from the upper 

 part of the previous year's shoot, where there is a larger supply of nutri- 

 ment. Again, leaves, in which the supply of food-material is limited, as a 

 rule produce roots only, but occasionally shoots from their basal portion. 



(4) Cheiaical Changes (including Fermentation). 



Formation of Albumen in Plants-t — According to Herr A. Emmerling, 

 the total amount of nitrogen increases during the first period of growth of 

 plants, especially in the leaves, until the commencement of the formation 

 of the seeds. From this time it remains nearly constant in the leaves, but 

 increases very rapidly in the fruits. The same is the case with the 

 albuminoids. The non-albuminous nitrogen decreases, as a rule, as the 

 amount of albuminoids increases, especially in the seeds and seed-vessels ; 

 while in the leaves it retains nearly the same proportion until the seeds 

 are ripe, but increases again, during the last stage, owing to retrogressive 

 metastasis. 



Of the non-albuminous nitrogenous constituents, the amido-acids occur 

 in especial abundance in the leaf-buds, floral organs, young seeds, and 

 seed-vessels. In the leaves the amount of these acids remains constant for 

 a long period, decreasing afterwards considerably ; and this is the case 

 also in the roots, seeds, and seed-vessels. From this it is seen that the 

 amido-acids formed in plants are gradually transformed into other nitro- 

 genous substances, and especially into albuminoids ; and that the capacity 

 of the plant to produce these acids decreases with age. 



The course of the formation of nitrogenous substances in Vicia Faha 

 appears to favour the hypothesis that the amido-acids are formed synthe- 

 tically in the plant, especially in the leaves, and that they are conveyed 

 to the plants where fresh formation of cells is taking place, such as the 

 growing-points and the seeds, where they are then transformed into 

 albuminoids. Since therefore it must be supposed that every young cell 



* Bot, Centralbl., xxxi. (1887) pp. 186-8, 220-3. 



t Landwirthsch. Versuchs-Stat., xxxi v. (1887) pp. 1-91. See Naturforscher, xx. 

 (1887) p. 267. 



