MOTION OF THE JUICES. 383 



In all cases, without exception, the matters organized 

 in the leaves, though most readily and abundantly mov- 

 ino 1 downwards in the vascular tissues, are not confined 



O * 



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 narrow 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 starch, 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 curbhydrates. 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 the incision, 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 nibbed or wiped with a cloth. 

 whereby the moist eambial layer (of eells containing nuclei and capa- 

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



