7i6 



CHEMICAL PROCESSES IN THE PLANT. 



endosperm which is then completely emptied and reduced to a thin membranous sac. 

 They now rise above the ground, become expanded to the light where they continue 

 to grow rapidly and become green, and serve from this period as the first assimilating 

 organs. 



In this case, as in the germination of all oily seeds, sugar and starch are produced 

 here in the parenchyma of every growing part, disappearing from them only when the 

 growth of the masses of tissue concerned has been completed. Since the endosperm 

 grows also independently, starch and sugar are, in accordance with the general rule, 

 temporarily produced in it. The cotyledons apparently absorb the oil as such out of 

 the endosperm, whence it is distributed into the parenchyma of the hypocotyledonary 

 portion of the stem and of the root, serving in the growing tissues as material for the 

 formation of starch and sugar, which on their part are only precursors in the pro- 

 duction of cellulose. In these processes of growth tannin is also formed which is of 

 no further use, but remains in isolated cells, where it collects apparently unchanged 



Fig. 4ji.—Ru-tm(s communist I longitudinal section of the ripe seed; //germinating seed with the cotyledons still 

 In the endosperm (shown more distinctly in A and B), s testa, e endosperm, c cotyledon, he hypocotyledonary portion 

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



until germination is completed. It can scarcely be doubted that the material for the 

 formation of this tannin is also derived from the oil of the endosperm, although perhaps 

 only after a series of metamorphoses. The absorption of oxygen, which is an essential 

 accompaniment of every process of growth and especially of germination, has in this 

 case, as in that of all oily seeds, an additional significance, inasmuch as the formation of 

 carbo-hydrates at the expense of the oil involves the appropriation of oxygen. 



Since the metamorphoses of material proceed pari passu with the growth of the 

 separate parts, the distribution of the products of metastasis through the tissues is 

 continually changing, and can only be understood by a consideration of all the sur- 

 rounding circumstances. The micro-chemical investigation of seedlings in the state 

 represented in Fig. 471 //, gives, for instance, the following result: — in the endo- 

 sperm is found a great deal of oil and a little starch, with sugar at the outside; the 

 epidermis and parenchyma of the slowly growing cotyledons are filled with drops of 

 oil ; a large number of the epidermal cells contain tannin ; starch-granules are found 



