MORPHOLOGY OF ANGIOSPERMS. 



101 



We have to distinguish between overground shoots and under- 

 ground shoots. The former are sometimes designated as epi- 

 geous (upon the earth) and the latter as hypogeous (under the 

 cartli ) . 



Epigeous Shoots. As woukl be supposed these two kinds 

 of shoots vary to a certain extent. In epigeous shoots a number 



Fig. 65 



G. 66. 



Fig. 65. Woody vine of Canada moonseed (Menispennum canadense), which ascends by 



twining to the right. 

 Fig. 66. Stem of wild yamroot {Dioscorea vtUosa), which ascends by twining to the left, 

 and bsveral of the characteristic 3-winged capsules at the top. 

 The twining movements of stem climbers are due to the stimulus of gravity rather 

 than to contact stimulus, and in the majority of twining plants the revolving movements, 

 as seen from the side, are from the left to the right, i.e., in a direction opposite to that of 

 the hands of a watch if represented diagrammatically. 



of features may be noted. If the internodes are long the leaves 

 do not usually interfere with one another so far as exposure to 

 light is concerned, but if the internodes are short, the leaves are 

 all brought close together on the axis, and hence were it not for 

 various modifications, their relation to light would be very 

 unequal. Sometimes the shoot-axis may share with the leaves 



