AMERICAN INSTITUTE. 449 



light, its internal structure may be clearly discerned. During fine weather 

 they are generally to be found on the surface of the water, in cloudy 

 weather at the bottom ; you may keep them alive indefinitely in vessels of 

 water, where they will increase rapidly in size. It preys upon live insects, 

 which you may often see attempting to get out of one of its stomachs, of 

 which it has a number, divided from each other by a transparent elastic 

 ring. Its digestive powers are extraordinary, as it often fills itself with 

 the hard shelled monoculi, and remains torpid while digestion is advancing. 

 This creature is found in the Croton, as well as the satyr, monoculi, vorti- 

 cclla, triehoda lyncens, common rotifier, guadricornus, water beetle, clos- 

 terium sunula, bell shaped, and numerous other animalcules. 



I have given much attention to microscopic examinations of woody fibi'e, 

 and have been particularly delighted with the study. The microscope de- 

 clares that all trees and plants consist of a woody portion, and pithy por- 

 tion. The woody portion is composed of an enormous number of small 

 tubes, commencing at the root and extending through numerous ramifica- 

 tions to every branch of the tree, numbering over seven millions to the 

 square inch, and are not arranged as I always supposed they were, through- 

 out the trunks, but are collected into bundles, numbering from thirty to 

 many Imudreds of tubes, arranged in regularly disposed concentric circles. 

 I imagined, until the microscope taught me difi'erently, that there were two 

 kinds of tubes in a tree — one to carry air, and the other sap, and that is 

 the reason why we have generally heard them called air vessels, and sap 

 vessels. I am now convinced that they are all sap vessels, and that there 

 are no air vessels in either trees or plants. These tubes are bound toge- 

 ther by a tissue, filled with cells, which is usually called cellular tissue. 

 The cells present to the microscope various forms, according to the plant 

 in which they are examined. Some are angular, some square, others 

 globular, triangular, but the greatest proportion are hexagonal. Some of 

 them are so exceedingly minute as to be observed with difficulty by the 

 most powerful microscope. The pith of a plant, or tree, consists almost 

 entirely of cells of diff"erent sizes. That in the Canada thistle, appears 

 about the size of honey comb cells ; that in the sumach, cherry, and pear, 

 are much smaller ; and in the oak, so minute that it would require 100 to 

 equal the pith of the thistle in size. 



Were it not for this admirable instrument, the microscope, the botanist 

 would be unable to reveal the beautiful structures of plants, and their 

 extraordinary interior organization, thegeologist would fail to read the 

 vegetable history of our world, which is plainly to be discerned in its 

 fossil plants and trees, with exquisite carved work, arranged with lon- 

 gitudinal lines, symmetrically wrought ; others are covered with scales, 

 like those of a fish, and provided with lids, which open like a hinge. 

 The butterfly produced by this egg, has wings perfectly resplendent 

 with the most brilliant colors, and when the dust, which attaches to 

 your fingers, on handling them, is examined with a microscope, presents 



[Am. Inst.] 29 



