96 



CONTENTS. 



trees, and in the larger shrubs, the bodies 

 of which are firm, and of strong, texture, 

 it is a ])art of little importance; but in the 

 reeds, the grasses, canes, and the plants 

 having hollow stalks, it is of great use, 

 and is exceedingly strong, and in the mi- 

 croscope seems composed of a kind of 

 glassy net-work, which is principally sili- 

 ceous earth. 



This is the case in wheat, in the oat, 

 in the different species of equisetum, and, 

 above all, in the rattan, the epidermis of 

 which contains a sufficient quantity of 

 flint to give light when struck by steel, 

 or two pieces rubbed together produce 

 sparks. This fact first occurred to me in 

 1798, and it led to experiments, by which 

 I ascertained that siliceous earth existed 

 generally in the epidermis of the hollow 

 plants. The siliceous epidermis serves as 

 a support, protects the bark from the ac- 

 tion of insects, and seems to perform a 

 part in the economy of these feeble vege- 

 table tribes, similar to that performed in 

 the animal kingdom by the shell of the 

 crustaceous insects. 



Immediately beneath the epidermis is 

 \\\Q parenchyma. It is a soft substance, 

 consisting of cells filled with fluid, having 

 almost always a greenish tint. The cells 

 in the parenchymatous part, when exam- 

 ined by the microscope, appear hexagon- 

 al. This form, indeed, is that usually af- 

 fected by the cellular membranes in vege- 

 tables, and it seems to be the result of the 



general reaction of the solid ))arts, similar 

 to that which takes place in the honey- 

 comb. 



This arrangement, which has been 

 usually ascribed to the skill and artifice of 

 the bee, seems, as Dr, Woolaston has ob- 

 served, to be merely the result of the me- 

 chanical laws which influence the pressure 

 of cylinders composed of soft materials, 

 <he nests of solitary bees being uniformly 

 circular. 



The innermost part of the bark is con- 

 stituted by the cortical layers, and their 

 numbers vary with the age of the tree. On 

 cutting the bark of a tree of several years 

 standing, the productions of different pe- 

 riods may be distinctly seen, though the 

 laj'er of every particular year can seldom 

 be accurately defined. 



The cortical layers are composed of 

 fibrous parts, which appear interwoven, 

 and which are transverse and longitudinal. 

 The transverse are membranous and po- 

 rous, and the longitudinal are generally 

 composed of tubes. 



The functions of the parenchymatous 

 and cortical parts of the bark are of great 

 importance. The tubes of the fibrous 

 parts appear to be the organs that receive 

 the sap; the cells seem destined for the ela- 

 boration of its parts, for the exposure of 

 them to the action of the atmosphere, and 

 the new matter is annually produced in 

 the spring, immediately on the inner sur- 

 face of the cortical layer of the last j'ear. 



CO»^^TE^TS of JYo. 6. 1*^1. M, of OISSESlT*JER A* RECORn, 



Morus jNlullicaulis and Silk. Culture, 81 



Silk Cultiue 82 



Early Corn, 84 



Potatoes raised tVom Cuttings, 84 



Silk Manufacture, 84 



Useful Hints, 84 



Cements, 85 



lleraedy for liurns, 87 



Remedy for VViiooping Cougli, , , 87 



Remedy for Squinting, 87 



Inflammatory Ulieuraatism, 88 



llurdock in Itiipetigo, 89 



Definition of Terms beginning witti the Letter D, 89 



Experiments in Boiling Wheat, 91 



Soiling Cattle, 91 



Chilblains, 92 



Sir H. Davy's Agricultural Chemistry, 94 



