PART OF MOVEMENT Of LIQUIDS IN PLANTS. 67 



irough which a colored solution has been lifted by transpiration, we can 

 le small groups of the minute cells in the cambial ring which are col- 

 red. These groups of cells which form strands running through the stem are 

 rocambium strands. The cells divide and increase just like the cambium 

 :11s, and the older ones thrown off on either side change, those toward the 

 :ntre of the stem to wood vessels and fibres, and those on the outer side to 

 ast cells and sieve tubes. 



123. Fibrovascular bundles in the Indian corn. — In fig. 54 is repre- 

 ssed a. fibrovascular bundle of the stem of the Indian corn. The large 

 :11s are those of the spiral and reticulated 

 id -annular vessels. This is the woody 

 artion of the bundle, or xylem. Oppo- 

 te. this is the bast portion or phloem, 

 arked by the lighter colored tissue at i. 

 he larger of these cells are the sieve 

 bes, and intermingled with them are 

 nailer cells with thin walls. Surround- 

 g the entire bundle are small cells with 

 ick walls. These are elongated and the 

 pering ends overlap. They are thus 

 :nder and long and form fibres. In 

 eh a bundle all of the cambium has 

 .ssed over into permanent tissue and the 

 indie is said to be closed. 



124. Rise of water in the vessels. — 

 uring the movement of the water or 



Fig- 54- 



Transection of fibrovascular bundle of 



Indian corn, a, toward periphery of 



stem ; g-, large pitted vessels ; j, spiral 



Ltrient solutions upward in the stem the vessel ; r, annular vessel ; /, air cavity 



. r ,. , ,. j. . . formed by breaking apart of the cells; 



ssels of the wood portion of the bundle i, so ft bast, a form of sieve tissue ; p, 



certain plants are nearly or quite filled, ^in-walled parenchyma. (Sachs.) 

 root pressure is active and transpiration is not very rapid. If, however, on 

 y days transpiration is in excess of root pressure, as often happens, the 

 ssels are not filled with the water, but are partly filled with certain gases 

 cause the air or other gases in the plant become rarefied as a result of the 

 cessive loss of water. There are then successive rows of air or gas bub- 

 ;s in the vessels separated by films of water which also line the walls of 

 ; vessels. The condition of the vessel is much like that of a glass tube 

 rough which one might pass the " froth" which is formed on the surface 



soapy water. This forms a chain of bubbles in the vessels. This chain 

 s been called Jamin's chain because of the discoverer. 

 125. Rise of water in the bundles is not we'l understood. — Why water or 

 id solutions can be raised by the plant to the height attained by some trees 

 s never been satisfactorily explained. There are several theories pro- 



