350 PRACTICAL BOTANY 



importation was only about 500,000 bunches. A few bananas 

 are grown in the Gulf States, but our main supply comes from 

 Jamaica and Central America. Entire trainloads of bananas 

 are shipped daily from New Orleans and Mobile to supply the 

 region west of the Mississippi as far as the extreme northwest, 

 and also some portions of the country east of the Mississippi. 

 Bananas differ from ordinary fruits in that they possess a 

 much higher nutritive value, so that they constitute a true 

 food which needs little supplementing to support life indefi- 

 nitely. They contain about three times as much protein and 

 one and a half times as much carbohydrates as do apples ; in 

 fact, a banana has about the same food value as a potato, con- 

 taining two thirds as much protein and a somewhat larger 

 quantity of carbohydrates. 



DICOTYLEDONS, CHORIPETALOUS SUB-CLASS 



317. Families of dicotyledons. There are about 34 orders 

 of dicotyledons, comprising 200 or more families. Of these 

 orders 26 belong to the choripetalous sub-class and 8 to the 

 sympetalous sub-class. The flowers of the choripetalous sub- 

 class have either no perianth, or one consisting of separate 

 sepals and petals (or sometimes of sepals only). The flowers 

 of the sympetalous sub-class have a sympetalous corolla. 



In this book only five of the most important among our 

 families of deciduous trees can be mentioned. Some other 

 facts in regard to them will be found in Chapter XXII. 

 Four of the other principal families will be briefly treated 

 here, namely,. the Rose family {Rosacece), the Pea family 

 {Leguminosce), the Spurge family (^Euphorbiacece), and the 

 Parsley family (Umbelliferce). 



318. Some families of hardwood trees. A large part of our 

 valuable hard wood comes from trees of four families, that 

 of the willows and poplars, that of the walnuts and hickories, 

 that of the oaks, chestnuts, and beeches, and that of the elms. 

 All of these except -the Elm family have unisexual flowers 



