276 



INTRODUCTION TO BOTANY 



f.is 



chlorophyll-containing tissues in such a position that they 

 may receive light ; at the same time, through the fibrovascu- 

 lar bundles of the leaf stock and the rhizome, soil water and 



substances in solution may be 

 transported to the chlorophyll 

 tissue. The root system an- 

 chors the plant in the earth 

 and absorbs the water needed 

 in food manufacture. 



In general, plants that rise 

 above the soil and into the air 

 must be supported and must 

 secure water from some source. 

 The climbing vines which are 

 dependent upon other plants 

 are supported chiefly by these 

 other plants. Most vines pro- 

 cure their supply of water 

 from the soil and transport it 

 by means of their own vascular 

 tissue. Fibrovascular tissue, 

 by reason of its strength, 

 makes possible the upright 

 position and is essential (as 

 is also the absorbing and an- 

 choring root system) alike to 

 the fields of upright grain and 

 to the forests. The importance 

 of vascular tissue in ferns 

 and higher plants can hardly 

 be over-estimated. 

 261. Types of ferns. Ferns are usually distinguished from 

 one another by the leaves, the sori, and the sporangia. There 

 is much variation in position and arrangement of sori in dif- 

 ferent ferns (fig. 215). In some the sori are dots placed regu- 

 larly upon the leaf. In others they are like slits or blistery 



FIG. 215. Types of fern leaflets 



A, bracken fern; B, shield fern; C, 

 spleenwort ; D, the maidenhair fern. In 

 the different specimens the sporangia 

 are at s, the indusium at i, and the false 

 indusium at f.i 



