116 



I JOT ANY 



have gradually arisen from the fundamental tissue in the course 

 of phylogenetic development. The fundamental tissue in the 

 higher plants is enclosed by tegumentary tissue, and traversed 1>v 

 the vascular bundle system. While the tegumentary tissue protects 

 the plant externally, and the vascular bundle system performs the 

 office of conduction, and also of mechanically strengthening the 

 plant, the duty of providing for the nutrition of the plant and of 

 storing reserve food material falls chiefly to the fundamental tissue. 

 The fundamental tissue consists, therefore, for the most part of 



parenchymatous cells containing chloro- 

 phyll, at least to such depth as the 

 light penetrates; internally a colourless 

 parenchyma is found. The fundamental 

 tissue system also takes part in pro- 

 viding for the mechanical rigidity of 

 plants, and in connection with this 

 function it possesses collenchyma (Fig. 

 74 c) and sclerenchyma as its special 

 mechanical tissues. -The COLLENCHYMA 

 (p. 68) is unlignified and very elastic, and 

 thus fitted for stretching ; it is the form 

 of mechanical tissue suitable for those 

 parts of plants still undergoing growth 

 in length. The sclerenchymatous fibres, 

 which are often unlignified but have 

 greatly thickened walls, on the other 

 hand, are formed after growth in length 

 has ceased, and sclereides (p. 73) arise 

 even later. The elongated cells of the 

 fundamental tissue also perform a certain 

 share of the work of conduction, and 

 serve for the transport of carbohydrates. Secondary or waste pro- 

 ducts, resulting from chemical changes, are also deposited in special 

 cells of the fundamental tissue. Consequently idioblasts (p. 73), 

 containing crystals or rows of crystal-containing cells, are often met 

 with in the fundamental tissues, together with cells, tubes, cavities, or 

 canals containing tannin, gum, resin, ethereal oils, latex, or alkaloids. 

 Such waste products are for the most part deposited near the surface 

 of a plant, in order to serve as a defence against destructive animals, 

 or that they may afterwards be thrown off along with the superficial 

 tissue. Cells containing these waste products, particularly crystal 

 cells and latex tubes, are often found, accompanying the phloem 

 portion of the vascular bundles. 



The Aroideae, Nymphaeaceae, and several other plant families possess a 

 peculiar form of idioblast, in the so-called internal hairs, which project into the 

 intercellular spaces of the fundamental tissue. In the wide intercellular passage* 



FIG. 126. Termination of a vascular 

 bundle in a ,leaf of Imputiens po,rvi 

 flora, (x 240.) 



