ASSIMILATION AND METASTASIS. 



639 



con parat.vely little oil but much starch and sugar; and a number of the cells of the 

 ep.dernus and parenchyma are filled with tannin. The primary root has first of all 

 completed its growth in length and thickness (after germination it begins afresh); in 

 Its lower part it contains neither starch nor sugar (the former is present in the root- 

 cap j ; in Its upper part from which the lateral roots spring and in the lateral roots 

 tnemselves sugar is also present, which is conveyed into the growing apices of the 

 latter. When the hypocotyledonary portion of the stem has subsequently taken a 

 direction straight upwards and ceases to grow, the oil, starch, and sugar have almost 

 entirely disappeared from it, and in their place the cell-walls have become thick, and 

 the vessels and first cells of the wood and bast are already thickened. After the stem 

 ot the young plant has become upright, the cotyledons expand and grow rapidly, and the 

 remainder of the oil which they had taken up from the endosperm now also disap- 

 pears trom them together with the starch and sugar. The seedling has now entered 

 on a state in which the non-nitrogenous reserve-materials are consumed; a framework 



Fig. AA^.-RiciHUS communis; I lonjjitudinal section of the ripe seed; // germinnting seed with the cotyledons still 

 «n the endosperm (shown more distinctly in A and B), s testa, e endotsperni, c cotyledon, Ac hypocotyledonary portion 

 of the stem, w primary root, w' secondary roots, x the caruncle. 



of large and solid cell-walls is produced in their place ; and a quantity of tannin remains 

 behind in some of the cells as a secondary product, as well as various other substances 

 not present in the seed. 



The albuminoids which form so peculiar and intimate a mixture with the oil in the 

 ripe seed, and which are partially contained in the aleurone-grains of the endosperm in the 

 form of crystalloids, are, during the processes which have been described, transferred 

 to the embryo, where they produce the protoplasm. During the whole of the period 

 of germination the cells of the fibro-vascular bundles are found to be densely filled with 

 albuminous mucilage, subsequently only those of the phloem ; these substances are 

 evidently in motion towards the apices of the roots \vhere new cells are continually 

 being formed. Every young rudiment of a lateral root behaves to reagents as an accu- 

 mulation of albuminous substance in contact with the fibro-vascular bundles of the 

 primary root. But a very considerable portion of this material remains in the upper 

 part of the stem of the seedling where new leaves are formed, and a still larger portion 

 in the cotyledons themselves, where it furnishes the material for the formation of the 

 numerous grains of chlorophyll. 



