ASSIMILATION AND METASTASIS. 
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 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 mature plant that the reser- 
voirs of reserve-material do for the seedling ; but with this difl'erence, 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-granules of plants that vegetate under 
normal conditions can only be produced when the plant is subject to the well- 
known conditions of assimilation, t. e. v/hen 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 Sei. 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. 
