

a. Root and shoot habit of Opuntia leptocaulis which was growing under the 

 protection of Acacia constricta, Tumamoc Hill. 



b. Opuntia versicolor showing habit of plant and character of environment. 

 A small specimen of Echinocactuswislizeni is to be seen at base of main stem. 



c. Bird's-eye view of a portion of the central part of the root-system of the 

 plant shown in b, with the overlying soil removed, leaving roots as far as 

 possible in their natural placing. 



d. This and figures on plate 11 are of one main lateral and some branches of 

 the plant shown above. 



