CHAPTER XVIII 



Locust, Coffee-bean and Red-bud 



A consideration of the locust^ and its allies introduces us to one 

 of the largest alliances of flowering plants, popularly known as the 

 Leguminosae, and now divided by botanists into four families. 

 These are the acacia or mimosa family (Mimosaceae) , the senna 

 family (Caesalpiniaceae), the krameria family (Krameriacece), and 

 the pea or bean family (Papilionaceas) . Among these there is a 

 well marked floral progression from the first, with its regular 

 flowers, to the last, with its butterfly-hke blossoms. The first 

 two families are very old geologically and are largely arborescent 

 foims of the Tropical Zone, many species of which have been found 

 fossil in the Tertiary deposits of our southern States. The last 

 two families, on the other hand, are mainly herbaceous forms 

 dwelling outside the tropics, and both have probably attained 

 their maximum of variation in the Temperate Zone since the in- 

 auguration of the Pleistocene glaciation. 



A large number of leguminous plants furnish most important 

 food or forage crops (peas, beans, lentil, peanut, tamarind, alfalfa, 

 clover, etc.) or are utilized in medicine (senna, licorice, etc.) or 

 other arts (indigo, logwood, gum tragacanth, gum arable, copaiba 

 gum, etc.). The habit of many of the Leguminosae of abstracting 

 nitrogen from the air by means of root bacteria makes them of 

 especial interest in these days of the rapid exhaustion of natural 

 nitrates. Many tropical Leguminosae are important timber trees 

 (brazil wood, iron wood, violet wood, etc.) but outside of local uses 

 the world's markets know but a few and these are found in the 

 cabinet maker's rather than in the lumber trade, and scarcely any 

 awaken a concept in the popular mind unless it be rosewood 



^ This is not the locust tree of southern Europe, which is the carob, Cecratonia 

 siliqua, a member of the Caesalpiniaceae. • 



191 



