ASSIMILATION AND METASTASIS. 601 



cane-sugar is stored up for the same purpose, inuline in the tubers of the dahlia 

 and starch in the tubers of the potato, the bulbs of the tulip, &c. ; and these are 

 subsequently consumed But in most seeds all these carbo-hydrates are replaced by 

 oily matter; and it cannot be doubted that this furnishes the material for the growth 

 of the cell-walls wlien the new organs are being formed. 



To the series of these substances of the same physiological value belongs finally 

 Ce/hdose itself, which may also be deposited in considerable quantities as a reserve- 

 material, as in the endosperm of the date, the greater part of the hard kernel of 

 which consists of cellulose in the form of dotted thickening-masses of the cell- 

 walls. These are dissolved during germination, and the products of their solution 

 conveyed to the growing parts of the embryo, where they finally supply the material 

 for the growth of the new cell-walls. 



If on the other hand the substances which occur in dormant seeds, bulbs, 

 tubers, and other reservoirs of reserve-material, are compared with those which are 

 found in the conducting tissues and growing organs of seedlings and young roots— 

 which we already know must necessarily be produced from the former, because there 

 is no other material which can produce them— it is seen that these reserve-materials 

 must undergo repeated Metamorphosis while they are being conveyed to the growing 

 organs and are being consumed in the process of growth, and before the permanent 

 form of cellulose has been attained. Thus sugar and starch are found temporarily 

 in all oily seeds during germination, and are often accumulated in great quantities, 

 disappearing when germination is completed. In proportion as they are formed the 

 amount of the original oil decreases ; and in proportion as they again disappear the 

 quantity of cellulose in the cell-walls increases. In other cases starch is conveyed 

 from reservoirs of reserve-material to the growing organs, sugar being at the same 

 time formed; and fine-grained starch is again temporarily formed in the growing 

 tissues themselves, disappearing once more with the growth of the cell-walls. This 

 temporary formation of starch in the growing tissues themselves is an extremely 

 common phenomenon, whether the reservoirs of reserve-material were filled with 

 oily matter, inuline, sugar, starch, or cellulose. This transitory starch appears in the 

 cells of the parenchyma and epidermis of young organs (only rarely in those of the 

 fibro-vascular bundles) after they have become differentiated from the primary meri- 

 stem ; and disappears when the final elongation of the organs is completed, generally 

 becoming transformed into sugar (glucose), which in its turn speedily disappears. 



Transitory metamorphoses appear to take place also when the albuminoids 

 stored up in the reservoirs of reserve-materials are being transported and con- 

 sumed ; although these metamorphoses cannot be followed by micro-chemical 

 observations, as in the case of the oils and carbo-hydrates. Thus a portion of 

 the caseine in the cotyledons of Leguminosse passes over into albumen during 

 germination ; the insoluble protein in the endosperm of wheat is 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 

 — ' ~~ " > 



' According to IIoskus, ammonia is also formed during germination ; and Uorscow maintains 



