MOTIOK OF THE JUtCES. 383 



In all cases, without exception, tlie matters organized 

 in the leaves, though most readily and abundantly mov- 

 ing downwards in the vascular tissues, are not confined 

 to them exclusively. When a ring of bark is removed 

 from a tree, the new cell-tissues, as well as the vascular, 

 are interrupted. Notwithstanding, matters are trans- 

 mitted downwards, through the older wood. When but 

 a narmo ring of bark is removed from a cutting, roots 

 often appear below the incision, though in less number, 

 and the new growth at the edges of a wound on the 

 trunk of a tree, though most copious above, is still de- 

 cided below — goes on, in fact, all around the gash. 



Both the cell-tissue and the vascular thus admit of 

 the transport of the nutritive matters- downwards. In 

 the former, the carbhydrates — stai-ch, sugar, inulin — the 

 fats, and acids, chiefly occur and move. In the large 

 ducts, air is contained, except when by vigorous root- 

 action the stem is surcharged with wacer. In the sieve- 

 ducts (cambium) are found the albuminoids, though not 

 unmixed with carbhydrates. If a tree have a deep gash 

 cut into its stem (but not reaching to the colored heart- 

 wood), growth is not suppressed on, either side of the 

 cut, but the nutritive matters of all kinds pass out of a 

 vertical direction around theincision, to nourish the new 

 wood above and below. Girdling a tree is not fatal, if 

 done in the spring or early summer when growth is rapid; 

 provided that the young cells, which form externally, 

 are protected from dryness and other destructive influ- 

 ences. An artificial bark, i. e., a covering of cloth or 

 clay to keep the exposed wood moist and away from air, 

 saves the tree until the wound heals over.* In these 

 cases it is obvious that the substances which commonly 

 preponderate in the sieve-ducts must pass through the 



• If the freshly exposed wood be rubbed or wiped with a cloth, 

 whereby the moist cambial layer (of cells containing nuclei and capa- 

 ble of multiplying) is removed, no growth can occur. Ratzeburg. 



