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VASCULAR PLANTS. 



I. THE ROOT. 



The root is less prone than any of the other organs 

 to deviate from the normal form, which is probably 

 cine to its usual location in the comparatively uniform 

 environment of the soil, where the factors which 

 induce variation are very much less numerous and 

 varied than they are above-ground. Most examples 

 of abnormal roots occur above-ground. 



The abnormalities in roots may be grouped under 

 four headings : (1) Branching ; (2) Fusion ; (3) 

 Change of Direction ; (4) Adventitious. 



1. BRANCHING. 

 M0N0P0DIAL. 



Those plants which have tap-roots, representing 

 the later development of the radicle of the seedling, 

 usually produce lateral roots of relatively insignificant 

 development which becomes still more marked when 

 the tap-root is swollen and fleshy. Owing to abortion 

 of or injury to the tap-root, or part of it, in the carrot 

 (Daucus Garoto), several of the lateral roots may 

 become very greatly developed, equalling in thickness 

 the original mother-root and often giving rise to 

 fantastically-shaped structures. Trecul describes in 

 the beet (Beta vulgaris) a lateral root which, owing 

 to its puncture by an insect, became greatly hyper- 

 trophied. Caspary figures a root of the rape (Bras- 

 sica Najpus) whose rootlets had developed as fleshy 

 tubercles. 



