GERMINATION. 461 



is so exceedingly distended, that the plumule is pushed from its 

 coverings and unfolded, whilst the summit of the cotyledons have 

 not yet left their envelopes. Where albumen is present, the 

 cotyledons often grow so rapidly within the envelopes, that they 

 consume all the albumen," whilst the entire embryo in the mature 

 seed takes up but a very small portion of space within it. Unim- 

 portant varieties in particular seeds are almost countless, and almost 

 every seed in germination exhibits its own peculiarities. 



With regard to the vital processes during germination, two phe- 

 nomena are to be distinguished, one of which has nothing to do 

 with the growth of the plant. 



At the time of the maturing of the seed, the cells of the embryo- 

 sac are usually filled with assimilated matter, whereby its shrinking 

 from the constant loss of water is prevented. The greater proportion 

 of this matter is not needed for the nourishment of the young 

 plant, and is subsequently destroyed, whilst the carbon of the 

 starch, oil, &c., is consumed at the expense of the atmospheric 

 oxygen taken up into the plant with the water, and is liberated in 

 the form of carbonic acid gas, whilst hydrogen and oxygen combine 

 to form water, and during these processes heat is given out. By 

 this means the cells become once more furnished with fluid contents, 

 and an active chemical life in their interior is again rendered 

 possible. The next consequence is the conversion of the remaining 

 substances into gums and sugars, which are then employed for the 

 formation of new cells. Mucus, as a catalytic substance, is doubt- 

 less active in the processes. 



A similar process to that in the embryo goes on in the albumen, 

 and the nutritious matter thus prepared is supplied to the embryo 

 through its surfaces. In many embryos, especially those of Mono- 

 cotyledons, the cells of the cotyledons become quite papillose, and 

 unite closely with similar papillose cells projecting from the inner 

 surface of the albumen. 



The testa, and the fruits enclosed in shells, according to some 

 specific peculiarity of their structure, sometimes exclude the entrance 

 of water, and so retard the process of germination ; and sometimes, 

 on the contrary, they accelerate it. 



We have already spoken of the morphological phenomena of 

 germination ; observations here have been so imperfect that they are 

 of little scientific value. 



We know nothing at all respecting the cause of the direction 

 taken by the germinating plant. Immediately the plant is exposed 

 to the light, it developes in its external parts chlorophyll. 



In order to understand the subject of germination, we must know the 

 structure of the seed. We find that it contains the rudiments of the future 

 plant, namely, a small body, having as essential parts a radicle and a 

 terminal bud. To these are added supplementary organs, which are used 

 at the end of the process of germination. These supplementary organs are 

 either the first leaves (cotyledons) or the albumen. In these we trace 

 three distinct relations, by means of which they subserve the purpose of re- 



