Ch. XVII] CLASSIFICATION. 103 
touch. Some vegetables, however, seem to have a kind of sen- 
sibility like that derived from the organs of touch in animals; 
they tremble and shrink back upon coming in contact with 
other substances; some turn themselves round to the sun, as if 
enjoying its rays. There is a mystery in these circumstances 
which we cannot penetrate; and it is not bh fully known at 
what point in the scale of existence animal life ends, and vege- 
table life commences. 
CHAPTER XVII. 
General Principles of Classtfication—Natural Families of 
Plants. 
420. Ler us now imagine the whole vegetable kingdom, 
comprising innumerable millions of individual plants, to be 
spread out before a botanist. Could he, in the course of the 
longest life, number each blade of grass, each little moss, each 
shrub, or even each tree? If he could not even count them, 
much less could he give each one a separate name and descrip- 
tion. But he does not need to name them separately, for he 
sees that nature has arranged them into sorts or kinds. 
431. If you were sent into the fields to gather flowers of a 
similar kind, you would need no book to direct you to put into 
one parcel, all the red clover blossoms, and into another, the 
white clover ; while the dandelions would form another group. 
These all constitute different species. Nature would also teach 
you that the red and white clover, although differing from each 
other in some particulars, yet bear a strong resemblance. 
432. By placing species together you form a genus, and to 
this genus you refer all the different kinds of clover. When 
you see red, damask, and cinnamon roses, you perceive they 
all have such strong marks of resemblance as to entitle them 
to be placed together in one genus. 
433, But yet you know that the seed of a damask rose would 
never produce a red rose. One species of plants can never 
eee another species, however near may be their resem- 
_blance. 
434. The whole number of species of plants which have 
430. Is it neeessary for the botanist to give a particular name to 
every plant? ; 
431. Do you ueed a book to teach you to put flowers of the same 
sort together ? ; 
432. How is a genus formed 2 
433. Does one species ever produce plants of another Species ? 
434, What number of species have been discovered 2 
