134 



FAMILIES OF FLOWEEING PLANTS 



" mesqnite " of Mexico and the soutliwestern States; the two species 

 occurring within our borders differ strikingly in their fruits, one (P. 

 pubescens) having the pods tuisted like a corkscrew, so that it is known 

 as screwbean. The true mesquite {P. juUflora), has long flattened pods 

 containing "beans" or seeds which are an important article in the 

 dietary of the average Mexican. 



The very large genus Acacia is represented in all tropical coun- 

 tries. A peculiar feature of its morphology is that the usually decom- 

 pound leaves, consisting of many leaflets, are in nearly all the Hawaiian 

 and Australian species reduced to flat bodies known as phyllodes, which 



look exactly like ordinary sim- 

 ple leaves, though somewhat 

 coriaceous (leathery) in tex- 

 ture, and standing vertical in- 

 stead of horizontal. The most 

 important economic product 

 jaelded by the genus is gum, 

 particularly gum-arabic; also, 

 the drug known as catechu. 

 Both these articles are derived 

 from the refined juice or sap. 

 Adenanthera pavonina, the red 

 sandalwood of tropical Asia, is 

 one of the most valued timber 

 trees of that region. Its bright 

 scarlet seeds, oddly enough, 

 are very uniform in weight, 

 each being 4 grains, and they 

 are therefore extensively used 

 by Oriental jewelers as weights. 

 While the shrubs and trees of 

 this family are not extensively 

 grown in our greenhouses, they 

 form a very important item in 

 tropical landscape gardening, 

 and in congenial situations they are of great size and beauty. The 

 group is probably more conspicuous in Australia than in any other 

 country. 



Family Caesalpiniaceae. Senna Family. Herbs, shrubs or trees, 

 comprised in about 90 genera and 1000 species, chiefly of tropical dis- 

 tribution. They are distinguished hj the nearly regular, often rosa- 

 ceous flowers, with. 5 sepals and 5 petals, the upi)er or odd petal en- 

 closed by the lateral ones; stamens 10 or fewer; fruit a pod. 



-^^f" 



From Coulter's Plant .Structures. Copyright, 1900, D 

 Appleton & Co. 



Fig. 116. A sensitive plant (Acacia), showing the 



flowers v.dth numerous stamens, and the pinnately 



compound leaves. After Meyer and Schumann. 



