92 



BOTANY AND PHARMACOGNOSY. 



The vegetative organs comprise the root and shoot, the latter 

 being usually differentiated into shoot axis or stem, and leaves. 

 The usual type of shoot is one which bears leaves and is exposed 

 to the light. The work of carbon dioxide assimilation (photosyn- 

 thesis) being carried on for the most part by the leaves, it is 

 sometimes spoken of as the " assimilation shoot." 



I. THE ROOT. 



True Roots are found only among plants having a vascular 

 system, as the Spermophytes and the higher Pteridophytes, 



Fig. 59. A, advanced stage of germination of the common garden pea {Pisum so- 

 Hvum) showing growing point of root protected by root-cap (p) ; root branches or second- 

 ary roots (rb) ; hypocotyl Che) ; epicotyl or stem above the cotyledons (ec) ; cotyledons 

 (one in view) (c). B, plantlet of white or yellow mustard (Sinapis alba) showing copious 

 development of root-hairs (h). 



although on the other hand some of the higher plants do not pos- 

 sess them, as certain of the Orchids. If we take a germinating 

 plant and mark the root or descending axis, lengthwise, by means 

 of a fine pen and India-ink, into ten equal divisions, beginning at 



