304 SYSTEMATIC BOTANY 



The fruit is nearly always a schizocarp or a loculi- 

 cidal capsule containing many seeds, which are often 

 forcibly ejected when it opens. 



The flowers are mostly regular, but in some, e.g. 

 TROPOEOLUM the garden Nasturtium, IMPATIENS the 

 Balsam, and PELARGONIUM the garden Geraneum (in 

 which it is adnate to the flower-stalk), one sepal is 

 spurred, and in the Balsam there appear to be only 

 three petals, because the lateral ones are united in 

 pairs, as the 'wings'. 



A very common well-known plant which belongs to 

 a family very nearly allied to the GERANIACE^E and 

 is well known to every one because of the small spiny 

 fruits, is TRIBULUS TERRESTRIS, L. a small weed 

 with prostrate, hirsute, branches, pinnate leaves, and 

 small yellow flowers. 



It differs from the GERANIACE^E in very little but 

 the fruit, whose spines assist in dispersal. 



TRIBULUS TERRESTRIS is a good instance of what 

 was said in chapter ix on the nature and distribution 

 of different types of plants (see p. 118). It occurs in 

 open sandy places where there is not much moisture 

 in the soil and the vegetation is not rich. 



Examples : 



CITRUS AURANTIUM, L., the Orange. The fruits 

 of varieties of this tree are the different kinds of 

 Orange. The ' Sweet Lime ' is the fruit of another 

 very similar species CITRUS MEDICA, L. 



This well-known tree has spiny branches and alter- 

 nate, exstipulate, one-foliate, leaves (see chapter xv, 



