26 THE NATURE AND WORK OF PLANTS 



large roots and the general shape of the root system. 

 What kinds of trees are most easily blown over? 



25. Roots were first developed for fixation. — In 

 the development of the plant world, roots were 

 first formed by the protoplasm for the purpose of 

 holding the organism in place, and in some of the 

 simpler forms of plants there are to be seen species 

 in which these organs serve no other purpose. The 

 ribbonlike bodies of the marine seaweeds, the lami- 

 narias which may be a foot, or several hundred feet, 

 in length, are fastened to the rocks by a system of 

 " holdfasts," not much larger than the hand. The 

 great extension of root systems to be seen in plants 

 growing in the soil is chiefly for the purpose of 

 absorption. If the root system of such a species is 

 carefully dug up, it will be found to penetrate the 

 soil to a depth of a few feet, and to extend out sev- 

 eral feet from the base of the stem. Indeed, the 

 total length of the root system generally exceeds 

 that of the stems and branches. It has been found 

 by actual measurement that the roots of a sun- 

 flower placed end to end would reach a distance 

 of hundreds, and those of a squash thousands, of 

 feet. 



