SUPPLEMENT 



The strength and flexibility of the stems of grasses have been 

 already noted. The leaves are usually well adapted to their environ- 

 ment, the species in humid climates being able to shed water because 

 of lines of wax, while many genera of drier regions have the power 

 of folding and unfolding their leaves to meet the varying conditions 

 of the atmosphere. Kerner devotes several beautifully illustrated 

 pages to this latter habit. The devices for the pollination of grasses are 

 very interesting, but they require close observation. In general, the 

 pair of feathery stigmas protrude from their wrappings for some 

 time before the anthers are allowed to escape; the bracts separate to 

 allow the exsertion of the anthers only under favorable conditions as 

 to temperature and moisture; as soon as the anthers are exposed, the 

 filaments lengthen almost as if by magic, attaining their full length 

 in a few minutes; the pollen is shaken from the suspended anthers in 

 the course of perhaps half an hour, though the empty cells may re- 

 main for a day or so. The fruits of grasses, or rather the bracts that 

 invest them, are frequently provided with barbed bristles, or awns, 

 that aid in seed distribution. The awns of several genera besides the 

 oats are hygrometric, the motion being spiral in the genus Stipa. 

 These awns, of course, serve the same purpose as the styles of the fil- 

 aree fruits. 



Identification of grasses is exceedingly difficult, but we have an 

 illustrated flora, the " Grasses of the South West." California has 

 some nutritious native grasses known as bunch grasses, but generally 

 our native grasses are not abundant and are yielding place to foreign 

 species, the most notable of which will be described in Chapter XVI. 

 No plant family can be compared with the grasses in economic value. 

 Rice, now universally cultivated in the tropics, feeds millions of the 

 human race, and wheat comes next. Wheat is supposed to have 

 originated in Asia, but it has been cultivated in Europe from prehis- 

 toric times. Barley and rye are probably of European origin; Indian 

 corn is American. Oats are of special value in countries with a brief 

 growing season. The cultivation of the sugar cane is still a leading 

 industry in warm countries; sorghum is nearly related to sugar cane, 

 and so is broom-corn The uses of the bamboo to the natives of trop- 

 ical Asia are well known. 



The Canna-banana group is tropical, but should be studied because 

 of its geographical importance. Sections of the apparent stems of 

 the banana, its flower clusters and young fruits are frequently acces- 

 sible. The apparent stem consists mainly of sheathing petioles; the 

 dark red bracts constitute the showy part of the flower cluster; 

 individual flowers have inferior, three-celled ovaries, six-parted 



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