Minnesota Plant Life. 



modified into a defensive armor. These plants indicate a strong 

 adaptation to desert life. "IMieir massive, leafless stems — leaf- 

 less in the sense of prodncing- no ordinary foliage leaves — sug- 

 gest the scantiness of the soil-moisture which they are able to 

 absorb, and because it is so hard to obtain, they have abandoned, 

 as far as possible, their evaporating surfaces. Some of them, 

 like the melon-cacti, have not only lost their foliage, but have 

 shortened their stems into spherical or ovoid melon-shaped 

 bodies. They have large roots, usually extending to a con- 

 siderable distance in all directions from the base of the stem. 



The strong defensive armor of 

 spines, which most varieties 

 possess, suggests a danger to 

 which the plants of an arid 

 region are exposed, owing to 

 the absence in such districts of 

 abundant forage for herb-eat- 

 ing animals. The three Min- 

 nesota species of prickly-pear 

 arc all of them wanderers from 

 tlie southwestern plains, where 

 iliey developed their peculiar, 

 characters, and now that they 

 have entered the more favor- 

 able northern region they re- 

 lain the o r g a n i z a t i o n best 

 adapted to their original home. 



Fig. 162. Western prickly-pear cactus. After 'r-vi , • ,- i • ..i 



Hritton and Brown. ^ '^^y are uot mtrcciuent m the 



Minnesota valley, on ledges of 

 rock near Xcw I Mm and Redwood Falls. One variety occurs 

 at Taylor's h'alls, in the valley of the St. Croix, while two are 

 abundant on the rocks in Pipestone county, in the \icinity of 

 the old Indian (|u<arr\'. Perhaps the Indians ha\e had some- 

 thing to do with their introduction from the soiuhwest. The 

 three species ma\' be distinguished by their spines and fr\iits. 

 The western prickly-pear produces a fleshy edible fruit, free 

 from spines, from one to two inches long, shaped somewhat like 

 a ])car, borne upon the tlat. sinuous joints of the stem. In this 

 \ariet\ llie spines i^n the stem are not numerous. 'iMiey occur 



