'i^iS CHEMICAL PROCESSES IN THE PLANT. 



what substances furnish the material for the produciion of cell-walls, protoplasm, 

 and grains of chlorophyll. Among the extraordinarily large number of the pro- 

 ducts of metastasis which are proved by chemical analysis to exist in various plants, 

 there are a comparatively small number of substances the behaviour of which in 

 the growth of the organs and whose universal distribution through the vegetable 

 kingdom clearly show that they furnish the material for the growth of cell-walls 

 and of other organised structures. These substances may be termed, without re- 

 ference to their chemical nature, Formative Materials. Starch, the different kinds 

 of sugar, inuline, and the fats must be considered the formative materials of the 

 cell-wall ; the albuminoids the formative materials of protoplasm and of the grains 

 of chlorophyll. 



Among the remaining products of metastasis are some which stand in genetic 

 relation to the production of sugar; the glucosides, to which also belong certain 

 tannin-substances. Asparagin is formed at the expense of the albuminoids con- 

 tained in the reservoirs of reserve-materials, and is afterwards again consumed in the 

 formation of albuminoids in the young organs. 



All those organic compounds may be termed Degradation-Products which are 

 produced by subsequent change in the substance of the organised structures of 

 plants, and which have no further use in the building up of new cell-walls or proto- 

 plasmic structures. Thus bassorin is a degradation-product of cell-walls, as also is 

 the mucilage of quince and linseed ; the substances which cause lignification, suber- 

 isation, or cuticularisation are also probably the result of a partial degradation of 

 the cellulose of the cell-walls. A residue of the protoplasm of older parenchy- 

 matous cells often remains until they entirely die away, and may also be considered 

 a degradation-product. In the same manner a small residue of the chlorophyll- 

 grains of leaves which die in the autumn remains over in the form of minute yellow 

 granules which have no further use. The red and yellow granules also which 

 cause the colour of ripe fruits and of the antheridia of Characeoe and Mosses, result 

 from the degradation of chlorophyll-grains, and have no further physiologico- 

 chemical use. 



Those substances may be termed Seco?tdary Products of Metastasis which are 

 formed during this change, but have no further use in the building up of new 

 cells, remaining inactive at the place where they are produced. Thus in the 

 germination of many seeds (the date, Ricinus, Phaseolus, Faba, &c.) tannin-like 

 compounds are formed in particular cells, and in many cases red colouring sub- 

 stances which, without undergoing any perceptible change, remain in these cells, 

 while the rest of the substances of the seedling go through the most various chemical 

 transformations and changes of place in the course of its growth. The same is the 

 function of the essential oils in the glands of leaves, of caoutchouc in the latici- 

 ferous vessels, of resin and resin-forming substances in the resin-passages, and of 

 the gummy compounds contained in the gum-passages of many plants. In this 

 category may also be included the greater number of vegetable acids and many 

 alkaloids. No interpretation has yet been given of the function of these substances 

 in the internal economy of the plant ; in the case of calcium oxalate Holzner's theory 

 has already been mentioned that it is formed as a secondary product when the 

 sulphuric acid combined with the calcium is replaced by oxalic acid ; and that the 



