t2 LECTURE X. 



Since Schmiedeberg, Drechsel, and others have succeeded in producing 

 proteid crystals artificially, we may infer that their formation in the plant 

 is not due to the organising activity of the protoplasm, but that it is a 

 process of ordinary crystallisation. 



When once deposited the reserve-materials undergo no 

 further change, or at most the proteids may slowly undergo 

 some alteration, so long as the organ in which they are de- 

 posited remains in an inactive condition. An organ in this 

 state is practically dead for the time being, all its metabolic 

 processes being arrested. It is capable, moreover, of resisting 

 injurious influences, such as extremes of temperature and 

 desiccation, which would prove fatal to it were it actively 

 living. It is obviously in consequence of this property pos- 

 sessed by such organs during what we may term their state 

 of suspended animation, that vegetation is maintained in re- 

 gions in which the cold of winter is severe and in arid tropical 

 regions. The time of the possible duration of this state with- 

 out permanent loss of vitality varies very widely ; spores, 

 for example, lose their power of resuming the active vital con- 

 dition, of germinating, in a word, in a comparatively short 

 time ; oily seeds retain the power of germinating for a much 

 shorter time than starchy seeds ; in some instances starchy 

 seeds have been known to retain it for many years. When 

 the external conditions become favourable, when the tempera- 

 ture is sufficiently high and there is a supply of water, these 

 quiescent organs readily germinate, and then the reserve- 

 materials which they contain undergo great chemical changes. 

 Germination is essentially connected with growth ; in a seed, 

 with the growth of the embryo ; in a bulb or a rhizome, 

 with the growth of a shoot. The chemical changes which 

 the reserve-materials undergo are of such a nature as to 

 convert them into substances which can readily travel to 

 the seat of growth, and which can be used as plastic material 

 by the growing cells. We will study these changes as they 

 occur in a seed. 



It has been observed by all who have investigated the 

 subject that, as the embryo grows, the reserve-materials in the 

 seed diminish in quantity. They are evidently conveyed to 



