PLANT STRUCTURE. o"6 1 



Now if we compare a mineral say a crystal of quartz with a plant, 

 we find the crystal uniform, consisting of small particles of quartz through- 

 out, and it appears an aggregation from outside of these particles in a 

 particular form. It cannot grow from within. But a plant can; and.it is 

 very different in structure and appearance. It receives nourishment from 

 outside also, but it assimilates the materials, which are not the same as those 

 we meet with in the plant itself. The mineral, on the contrary, is essentially 

 the same throughout ; it can only grow by aggregation of atoms like itself. 

 A plant, therefore, like an animal, must have organs within it, and must be 

 capable of change in itself ; it has powers of reproduction, and in some few 

 instances of locomotion ; it can eat flies, and assimilate them as an animal 

 does. 



A plant, therefore, is an organized body without external voluntary 

 movement ; and hereby it is essentially distinct from an animal, with which, 

 in organization, it is closely connected. The simplest form of the animal 

 as of the plant, is that of a minute vesicle or cell, containing a fluid in 

 which are some granular substances. At this stage it could not be dis- 

 tinguished from the simplest plant, if it had not the faculty of voluntary 

 movement the power of changing its place. The animal has a locomotive 

 power. Sometimes, indeed, it is a very limited sphere to which it is con- 

 fined ; yet it may change its place for another more conducive to the 

 exigencies of its being. 



It is sufficient for the present to have given the most general character- 

 istics by which plants are distinguished from the other objects that, with 

 them, compose the great kingdom of Nature. A precise and clear appre- 

 hension of their varied forms and wonderful phenomena can only be obtained 

 by a careful analysis of the nature and structure of the subjects of the vege- 

 table kingdom. 



The cell is the fundamental or elementary organ of plants, and the 

 knowledge of its metamorphoses and functions constitutes the foundation 

 of botany. We must therefore first consider the simple organs of plants. 



STRUCTURE OF PLANTS. 



It will be necessary for the reader to gain some little knowledge of the 

 tissues and cells of plants before he proceeds to examine the organs of 

 development, and a microscopic examination will soon disclose the few simple 

 tissues which are termed cells and vessels. These exist in all plants of 

 whatever nature. Plants are aggregations of cells, "every one of which has 

 its little particle of protoplasm enclosed by a casing of the substance called 

 cellulose, a non-nitrogenous substance nearly allied in chemical composition 

 to starch." * The tissues are " cellular " and " vascular " respectively. 



The cells have an outer sac or covering which is transparent, and this 

 cover is the cellulose above mentioned. It contains (i) the protoplasm, a 



* Dr. Carpenter. 



