102 NuttalVs Introdaction to Botany. 



genus always rests satisfied with bringing together such sub* 

 ordinate groups only, as are clearly natural ; or, while they 

 agree in the structure of flower and fruit, only differ specifical- 

 ly, in the minor consideration of the forms of leaves, petals, 

 appendages, or slight modifications of parts. It cannot be de- 

 nied, that, however anxious the systematic botanist may be 

 to draw nice distinctions among kindred genera and species, 

 yet when he proves so fortunate as to become acquainted with 

 a perfect group of natural or resembling genera, and approxi- 

 mating species, he cannot often help observing such an inter- 

 linking, and gradual passage of one modification of form into 

 another, as to lead to the belief that such divisions as genera 

 and species, though generally convenient and lucid in ar- 

 rangement, are often not really in the original plan of nature, 

 which ever delights in slender shadows of distinction, and 

 while uniting, yet contrives to vary with an infinite diversity, 

 the tribes of her numerous kingdom." pp. 43, 44. 



The second part of the work is devoted to the Physiology 

 of Plants, and consists of five chapters : with the first of these, 

 containing some very interesting remarks upon the general 

 character of plants, we shall close our extracts. 



" Besides the consideration of plants as mere objects of a 

 system and holding a relation to each other, they deserve a 

 higher regard as forming an eminent part of living and or- 

 ganized nature. Like animals, they are subjects of life and 

 death, and only differ essentially from that higher order of 

 beings in the want of evident sensibility ; for the few apparent 

 and equivocal exceptions to this universal rule, in the plants 

 termed sensitive, do not militate against its general applica- 

 tion. Nothing like nerves, or a nervous sensorium is to be 

 found in the vegetable kingdom, and, consequently, no dis- 

 play of that motion, energy, or irritability, which belongs to 

 the government of the different senses. The propulsion of 

 the sap, derived alone from a fluid papulum, and its elabora- 

 tion, in the vegetable tissue, into which it immediately enters, 

 appears at once the simple source and cause, of all that inap- 

 preciable motion in this tribe of beings, which we term growth 

 or developement. 



" The display of vegetable vitality, is, in many instances, 

 periodical. In those plants which we indefinitely term an- 

 nuals, the whole period of existence terminates in a few 

 months, and from the seed alone, is then to be obtained a 

 new generation of the species. But in our perennial plants, 



