78 VIEWS OF THE MICROSCOPIC WORLD. 



CHAPTER IV. 



OF THE STRUCTURE OF WOOD AND HERBS. 



I read His awful name emblazoned high 

 With golden letters on the illumined sky ; 

 Nor less the my&ic characters I see 

 Wrought in each flower, inscribed on every tree. 



BABBAULD. 



NATURALISTS have discovered by the aid of the microscope that all plants 

 consist of two kinds of organic matter, essentially distinct, the woody portion 

 and the pithy portion ; and that the several parts of a plant, however differing from 

 each other in form, texture, and appearance, are still composed of the same two 

 substances, but varying in the proportion and arrangement. The woody portion has 

 also received the name of the vascular system, while to the other division has been 

 assigned the appellation of the cellular tissue ; and these will now be described, 

 so far as is necessary for the purpose of this work, without any design of enter- 

 ing fully into the subject of vegetable anatomy. 



WOODY PORTION. The woody part of a plant, whether herb or tree, is not 

 solid, but is composed of a vast number of small tubes, extending from the 

 roots, and ramifying through the stem and branches to every part of the plant ; 

 even the oldest and most compact species of wood is nothing else than a collec- 

 tion of vessels and cells, the sides of which consist of extremely thin and delicate 

 membranes. 



In the more highly organized animals, the vital fluid is distributed through 

 appropriate channels by the action of the heart, throughout every part of the 

 body. Near the heart these conduits are large, and few in number, but decrease 

 in size and become less numerous as they are more remotely situated. In plants 

 no such central fountain exists, but the fluids necessary for their life and devel- 

 opment, entering from the soil through countless mouths at the roots, flow 

 upward along the minute tubes of the plants, and are disseminated to every 

 part where their presence is needed. The form of these tubes is generally 

 cylindrical, and much difference exists in respect to their size. On account of 

 the great minuteness of these pores it is extremely difficult to estimate their 

 number correctly. An approximation to the truth may, however, be attained by 

 first driving off the fluid that fills the pores, without destroying their figure, as 

 is done in the preparation of charcoal, and then examining a cross section 

 with a microscope. This method was pursued by Hooke, who numbered in a 



