632 CHEMICAL PROCESSES IN THE PLANT. 



the decomposition of the albuminoids under the influence of the energetic oxidation 

 which takes place in the germinating seed, i. e. in the growing parts of the embryo, 

 are again consumed in the formation of albuminoids. 



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 substances 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 plant that the reservoirs 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 ; oily matter perhaps occasionally. It has been shown (p. 46) that the starch 

 which so commonly occurs in the chlorophyll-grains 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, and 

 these 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 grains of chlorophyll disappears in the dark ; i. e. becomes 

 dissolved and transferred to the conducting tissues. In Allium Cepa the chloro- 

 phyll 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. 

 Where drops of oil are found in the chlorophyll, they appear to be first of all formed 

 at the expense of the starch which has been produced there; this conclusion being 

 derived especially from the observation of what takes place in Spirogyra. 



The result of tracing by micro-chemical observation the products of assimila- 

 tion in the conducting tissues leads once more to the conclusion that the starch 

 which is formed in the cells containing chlorophyll is subject to a variety of 

 chemical metamorphoses before it reaches the growing tissues and the reservoirs of 

 reserve-material. Even during the period of vegetation the substances w^hich are 



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

 imp. des Sci. Nat., Petcrshourg, vol. VII, 1S68). This is however denied by Wolf and Zimniermann 

 (Bot. Zcitg. 1871, nos. 18, 19). 



