Ilevieics. — Lindhy''s Theory of Ilorticullurc. 21 



transmission of this fluid, through or between the sides of the woody 

 tissue. So when "ringing" is practised, and the alburnum is partial- 

 ly destroyed, the ascending fluid diverges into the straluni of wood 

 beneath the annulation; and, when it has jiassed by, it again returns 

 into its accustomed channels; at the same time, it is probable, 

 although not proved, that some portion of the descending sap forces 

 its way laterally below the wound, out of the bark into the alburnum, 

 using the latter as a means of communicating with the bark below 

 the ring. 



Some curious experiments upon this subject were contrived by Mr. 

 N. Niven, {Gardener's Magazine, vol. xiv.) In one case, he di- 

 vested the stem of a tree of a deep ring of bark, and of the first 

 twelve layers of wood below it; nevertheless the tree continued to 

 live and be health}'. From the exposed surface of the wood no sap 

 made its appearance, except from a cut which had been inadvertently 

 made with the saw on one side, to the de])th of, perhaps, five or six 

 layers of wood beyond the twelve actually removed. From that cut 

 a flow of sap took place, and continued to run during the whole of 

 the season in which the operation was performed. In this case, the 

 sap must have ascended exclusively by the alburnum.* 



We would invite attention to the wonderful economy of 

 leaves, and the beautiful deduction relative to the probable 

 habits, as applicable to the culture of plants. 



A leaf has moreover a skin, or epidermis, drawn all over it. This 

 epidermis is often separable, and is composed of an infinite number 

 of minute cavities, originally filled with fluid, but eventually dry and 

 filled with air. In plants growing naturally in damp or shady places 

 it is very thin; in others, inhabiting hot, dry, exposed situations, it is 

 very hard and thick; and its texture varies between the two ex- 

 tremes, according to the nature of the species. The epidermis is 

 pierced by numerous invisible pores, called stomates, through which 

 the plant breathes and perspires. Such stomates are generally larg- 

 est and most abundant in plants which inhabit damp and shady 

 places, and which are able to ])rocure at all times an abundance of 

 liquid food; they are fewest and least active under the opposite con- 

 ditions. It will be obvious, that, in both these cases, the structure of 

 a leaf is adjipted to the peculiar circumstances under which the plant 

 to which it belongs naturally grows. Now, as this structure is capa- 

 ble of being ascertained by actual inspection with a microscope, it 



* This is a possible case ; but the American, familiar with the practice of girdling 

 trees, (which is nothing more than ringing with the hatchet,) so common in the new 

 settlements, well knows that it destroys vitality as certainly as cutting down the tree 

 at once. — During the deep snows of winter, in the nortliern States, young apple- 

 orchards are often destroyed by field mice, wliich girdle the trees near tlie ground, and 

 they perish in the course of the ensuing season. The trees may however be preserved, 

 by taking a suitable circle or section of bark, in tho spring, from the limb of another 

 apple tree, and adapting it carefully to the wounded bark, the edges of which are to 

 be pared to an even line, and the whole bound up and covered with grafting clay. It 

 is not absolutely necessary that the bark intioduced should encompass the whole trunk ; 

 as the union by a single portion will preserve the life of the tree, and the remainder of 

 the wound will gradually become covered with new bark. A. J. D. 



