INTRODUCTION. 



erties may continue after death. Secondly, those which 

 relate to their vitality ; such as contractibility : which, 

 consequently, can exist only in the living state. 



The organs of vegetables are all composed of a mem- 

 branous tissue, which pervades the whole of the plant ; 

 they are distinguished by the name of elementary, and 

 are of three kinds. 



1st. The cellular system, consisting of a fine tissue 

 of minute cells or vesicles, of a haxogonal form, appa- 

 rently closed and separated by thin partitions, somewhat 

 similar to the construction of a honeycomb ; or bearing, 

 perhaps, a still nearer resemblance to the bubbles formed 

 by the froth of beer. 



Emily. This appears very similar to the cellular sys- 

 tem in the animal economy, which you described to us 

 .n our lessons on Chemistry. 



Mrs. B. One of the chiefpurposes of the cellular sys- 

 tem in the animal frame is to contain the fat, a substance 

 to which there is nothing analagous in the vegetable 

 kingdom. 



These cells in plants, are marked by small spots, which 

 have been conjectured to be apertures through which 

 fluids are transmitted from one cell to another; but these 

 jnarks are so very minute, as to render it hazardous to 

 venture on deciding fbr what purpose they are designed. 



Caroline. If it is the cellular system which transmits 

 the sap, it should with more propriety be compared to 

 the veins and arteries of animals. But are not plants 

 furnished also with a vascular system ? 



Mrs. B. Yes ; and this forms the second set of ele- 

 mentary organs. It consists of tubes open at both ends : 

 these are always situated internally, and are, besides, 

 guarded from injury by being lodged in a thick coating 

 of the cellular integument. Some of these vessels assume 

 the form of a necklace, their coats being at intervals drawn 

 tight together, or strangulated, so as to appear to stop 

 the passage of the fluid they contain. 



59. Of what are the organs of vegetables composed; how are they 

 distinguished; and of how many kinds are they 1 ? 60. How may the 

 first kind be described 1 ? 61. For what purpose is the cellular system 

 in animals'? 62. What is said of the cells in plants'? 63. What 

 does Caroline call the second set of elementary organs'? 64. Of what 

 4o they consist, and how are they described'? 



