20 



INTERCELLULAR PASSAGES. 



Fig. 20. 



Lactiferous tissue. 



Cinenchyma, or Lactiferous Tissue. 



32. Cinenchyma, Fig. 20, is a tissue that consists of minute 

 tubes anastomosing with each other, and arranged in no definite 

 direction, in reference to the other tissues. 

 The tubes are of very different diameter in 

 different parts. The vessels generally take a 

 waving direction, seldom proceeding in a 

 straight line. The tubes become thickened in 

 age by the deposition of new matter. The 

 cinenchyma is found in greatest abundance in 

 the liber of the bark, across the parenchyma 

 of the leaves; but, no doubt, exists in almost 

 every part of flowering plants. It has been 

 detected in the pith, in the bark of the roots, 

 in connection with the spiral vessels, and, it is 

 said, in the cells of hairs. We have readily 

 detected this tissue in the liber of a vigorous Fig, in w r hich the 

 vessels were distended with fluid. This tissue is called the 

 Lactiferous, from the circumstance of its containing the milky 

 juices of plants. When the Fig, Lettuce, Asclepias, and Euphor- 

 bia are wounded, a milky juice immediately issues ; this pro- 

 ceeds from the severed vessels of the cinenchyma. Although in 

 these cases the latex (the name of the fluid contained in this 

 system of vessels) is white, in others it is colorless, and in some 

 yellow. It has been thought to.be the most highly elaborated 

 juice of the plant. It is doubted by some of the most distin- 

 guished philosophers whether these are originally tubes or not. 

 They think them intercellular passages that become lined with 

 membrane, and that the latex, so far from being the highly 

 elaborated sap destined for the nourishment of the planty is in 

 reality a substance eliminated, unfit for the use of the plant. 



We have given above the forms of tissue which make up 

 eveiy vegetable, from the humblest plant to the largest tree of 

 the forest. 



INTERCELLULAR PASSAGES. 



33. In placing together the various tissues, which are either 

 globular or cylindrical, spaces are necessarily left between the 

 walls of adjacent cells or tubes, which are called intercellular 

 passages. The appearance on a large scale may be illustrated 



82. Of what docs the lactiferous tissue consist ? Where found in greatest 

 abundance? Why called lactiferous? What doubt about it? — 33. What 

 are intercellular passages if 



