HENFRETS BOTANY. 81 



The study of affinities is neither guess-work nor divination, 

 but a matter of logical deduction from structure, based upon 

 scientific principles, — principles recognized and acted upon 

 by sound botanists with considerable unanimity, although 

 they have never been reduced to a system, nor expounded in 

 detail, so as to make them matters of elementary instruction. 

 Until this desideratum is supplied, the young botanist can do 

 no better than to take as models the writings of Brown, and 

 of those botanists who, according to their ability, have most 

 closely followed the footsteps of this master in science. 



Having continued this review far beyond our intention at 

 the outset, we have small space left for noticing the best part 

 of Professor Henfrey's treatise, namely, the third or Physio- 

 logical part. Suffice it to say, that, in the important chapter 

 on the physiological anatomy of plants, our author writes 

 from the fullness of his acquaintance with the writings and 

 doings of all the continental phytotomists, and also with the 

 authority of an experienced original investigator. And, so 

 far as we know, it comprises much the best resume of vege- 

 table anatomy and development now extant in the English 

 language, at once succinct, clear, trustworthy, and well brought 

 up to the present state of the science. Perhaps the succeed- 

 ing chapters, on the Physiology of Plants generally, the Phys- 

 iology of Vegetation, and on Reproduction, are equally com- 

 mendable in their way ; but we have as yet barely glanced 

 over the pages. We like the following definition, and the 

 ensuing paragraph upon the role of vitality in plants. 



" The physiology of plants is that department of botany in 

 which we investigate the phenomena of the life of plants, 

 manifested in a series of changes taking place in the diverse 

 parts of which each plant is composed " — (p. 475). 



" The physiological phenomena which indicate vitality are 

 always of more or less complex nature, and admit of being 

 analyzed into a number of factors, of which a large propor- 

 tion are found to be purely physical or chemical. A very 

 considerable part of the changes which accompany the process 

 of organization are the results of the action of physical and 

 chemical forces, [and] capable of being explained up to a 



