' 





PREFACE. 



THE two volumes on Cryptogamous and Phanerogamous 

 plants already published by the author, were written with an 

 " especial reference to the wants of medical students and phy- 

 sicians." Botany has not yet obtained that position to which 

 it is deservedly entitled, as a preparatory study to the organo- 

 graphy and physiology of animals. It is still excluded from 

 the most important medical schools ; and this state of things 

 will continue despite of all the efforts of botanists, so long as 

 the plant is regarded as if it were isolated from the rest of 

 organic nature. 



The functions of animal life appear to be gradually super- 

 added to those which are strictly vegetative. As we pass 

 from the plant through the coral and sponge to the higher 

 order of animals, bones, blood-vessels and nerves, gradually 

 appear ; the organs of the senses become more perfect, and the 

 motions more complicated, until at length in man, the nervo- 

 muscular system, which has thus been gradually, superadded 

 to the vegetative, manifests itself most perfectly in all that 

 infinite variety of movement and sensation peculiar to rational 

 beings. On the other hand, as we descend from man to ani- 

 mals still lower in the scale of creation, in proportion as the 



