ASSIMILATION AND METASTASIS. 709 



case of the oils and carbo-hydrates. Thus a portion of the casein in the cotyledons 

 of Leguminosae passes over into albumin during germination ; the insoluble proteids 

 in the endosperm of Wheat are dissolved and carried up into the seedling plant. 

 The albuminoids contained in seeds appear to be subject during germination to Still 

 more complete decompositions. The asparagin which occurs temporarily in parts 

 of the embryo can only be formed by partial decomposition of the albuminoids ^. 

 It appears however that these products of the decomposition of the albuminoids 

 under the influence of the energetic Oxidation which takes place in the germinating 

 seed are used in the formation of albuminoids in the growing parts of the embryo. 



The preceding remarks refer to the processes of growth which are associated 

 with the consumption of the substances stored up in the reservoirs of reserve- 

 material. If those plants are now examined in a similar manner whose reserve food- 

 material has been consumed, whose green leaves have begun to assimilate under the 

 influence of light, and which are forming the substan'=^^ necessary for the growth 

 of their buds, roots, &c., the same substances are found similarly distributed through 

 the conducting tissues of the internodes and the petioles and veins of the leaves as 

 far as the buds and apices of the roots, and subject to the same metamorphoses as 

 in the seedlings. It follows that the assimilating organs which contain chlorophyll 

 perform the same function for the growing parts of the mature plant that the reser- 

 voirs of reserve-material do for the seedling ; but with this difference, that the former 

 produce the formative materials afresh, while in the latter they are not formed but 

 only stored up. 



The organic compounds originally formed in the cells containing chlorophyll 

 by the decomposition of carbon dioxide and water under the influence of light are 

 generally carbo-hydrates. The most common of these is starch ; sugar occurs less 

 often j oily matter perhaps occasionally. It has been shown (p. 46) that the starch 

 which so commonly occurs in the chlorophyll-granules of plants that vegetate under 

 normal conditions can only be produced when the plant is subject to the well- 

 known conditions of assimilation, i. e. when it decomposes carbon dioxide and water 

 under the influence of sunlight. Seedlings which have completely exhausted their 

 supply of reserve-materials by growth in the dark, and are afterwards exposed to the 

 action of light, do not till then develope their chlorophyll. The first grains of starch 

 which are found a little later in the plant are those enclosed in the chlorophyll- 

 granules, and are at first small, but gradually grow larger. It is only afterwards that 

 starch is found also in the conducting tissues of the internodes and leaf-stalks up to 

 the buds, which then begin to grow anew. It has been shown further that this 

 starch which is formed in the chlorophyll-granules disappears in the dark ; i. e. be- 

 comes dissolved and transferred to the conducting tissues. In Allium Cepa the 

 chlorophyll forms no starch ; but a substance similar to grape-sugar is found in 

 large quantities in the green leaves, and is distributed through all the tissues of the 

 plant : it is still uncertain whether or not mannite is formed in a similar manner in 

 the leaves of the Olive. Where drops of oil are found in the chlorophyll, they appear 



^ According to Hosseus, ammonia is also formed during germination ; and Borscow maintains 

 that ammonia is set free during the vegetation of Fungi (Melanges biol. tires du Bullet, de I'Acad, 

 imp. des Sci. Nat. Petersbourg, vol. VII, 1868). This is however denied by Wolf and Zimmermann 

 (Bot. Zeitg. 1871, nos. 18, 19). For a further account of Asparagin see the appendix to this section. 



