e^fi CHEMICAL PROCESSES IN THE PLANT. 



I infer, even where we have to do with closed cells, from the fact that considerable 

 quantities of the cell - sap appear on the surface of a transverse section of 

 succulent organs, both from the parenchyma and from the cambiform cells, and 

 this is clearly forced up by internal pressure. Since the tension and turgescence 

 of the tissue are always less in the buds and apices of the roots than in the older 

 parts, there must always be a tendency for the filtration of the sap towards the 

 latter, which must act in the same way as diffusion. 



That the contents of the perforated sieve-tubes and laticiferous vessels are 

 also subject to considerable pressure from the surrounding tissue is shown by 

 the extent to which these fluids flow out when the organ is cut through. The 

 fluid which is subject to pressure will have a tendency to escape from these tubes 

 to parts of the plant where the lateral pressure is less, which is the case in the 

 buds and apices of the roots. The flexions and distortions occasioned in the 

 organ by the wind wifl at the same time cause the fluid contents of the sieve- 

 tubes and laticiferous vessels to be pressed away from the older bent parts towards 

 the buds where the tension is less. 



The statements here compressed into a very brief space rest on a series of detailed 

 micro-chemical and experimental researches which I have described in the Botanische 

 Zeitung, 1859 and 1862-1865; Pringsheim's Jahrbiicher fiir wissenschaftliche Botanik, 

 Vol. 111. p. 183 et seq.\ Flora, 1862, pp. 129 and 289, and 1863, pp. 33 and 193 ; and have 

 presented in a connected form in the section on the Transformation of Food- materials in 

 my Handbook of Experimental Physiology ^ The reader \\\\\ there find the reasons for 

 the views here given ; and a few examples will now be sufficient to render somewhat 

 clearer the general statements with regard to metastasis and the migration of the assim- 

 ilated substances. In the outset it must be stated that by grape-sugar or simply sugar 

 I understand a substance soluble in the cell-sap, easily reducing copper oxide, and 

 readily soluble in strong alcohol, although it may not always exactly correspond to the 

 grape-sugar of chemists, a point which is of but little importance for our present 

 purpose. 



The parenchyma of the bulb-scales of the tulip — /. e. the four or five thick 

 colourless leaves which serve as reservoirs of reserve-material — contains, as long as the 

 plant is dormant, in addition to considerable quantities of mucilaginous albluninoids, 

 a very large quantity of coarse-grained starch. The presence of sugar cannot be 

 determined at this time by micro-chemical processes. As soon as the bud of the 

 leaf- and flower-stem which is concealed within the bulb, but had already been formed 

 with all the parts of the flower during the previous summer, begins to elongate in 

 February, and roots make their appearance from the base of the bulb, small quantities 

 of sugar are found with the starch in the parenchyma of the bulb-scales. The whole 

 of the parenchyma and of the epidermis of the leafy stem, of the young foliage-leaves, 

 of the perianth, of the stamens, and of the carpels, becomes filled with fine-grained 

 starch, the substance of which has already been derived from the bulb-scales, where 

 the starch-grains have become transformed into sugar, which diffuses into the growing 

 organs, and there, as far as it is not directly consumed, again supplies material for the 

 formation of starch-grains. 



Together with its consumption in the growth, at first slow, of the cell-walls, this 

 temporary re-formation of starch at the expense of that contained in the bulb-scales 



^ The recent researches of Schroder (Jahrb. fiir wiss. Bot, Vol. VII, p. 261), Soraurer, Siewert, 

 Roestell &c., (collected in Hoffmann and Peters' Annual Report on the Progress of Agricultural 

 Chemistry for i?68 and 1S69, Berlin 1871) contain fresh confirmations of the account here given. 



