20O PROCESS OF BEVELOPEMENT. CHAP. IV. 



but one act of the vital principle, the parts being 

 all unfolded in immediate succession and without 

 any perceptible interruption till the plant is com- 

 plete. In the latter, the process is carried on by 

 gradual and definite stages easily cognizable to the 

 senses, commencing with the approach of spring, 

 and terminating with the approach of winter ; 

 during which, the functions of the vital principle 

 seem to be altogether suspended, till it is aroused 

 again into action by the warmth of the succeeding 

 spring. The illustration of the latter, however, 

 involves also that of the former; because the growth 

 of the 6rst year exemplifies at the same time the 

 growth of annuals, while the growth of succeeding 

 years exemplifies whatever is peculiar to perennials, 



SECTION I. 

 Elementary Organs. 



IF the embryo, on its escape from the seed and 

 conversion into a plant, is taken and minutely in- 

 spected, it will be found to consist of a root, plume- 

 let, and incipient stem, which have been developed 

 in consecutive order ; and if the plant is taken and 

 dissected at this period of its growth it will be found 

 to be composed merely of an epidermis enveloping 

 a soft and pulpy substance, that forms the mass of 

 the individual ; or it may be furnished also with a 

 central and longitudinal fibre ; or with bundles of 



