LESSONS IN BOTANY. 235 



resembling an outer calyx. In the mallow family the calyx is 

 valvate and the corolla convolute in the bud. By valvate is 

 meant that the edges of the parts meet without overlapping or 

 infolding, while in the convolute arrangement one edge of each 

 leaf covers one edge of the next, so that each leaf has one cov- 

 ered and one free edge. A cross section of a bud of a mallow 

 blossom shows these arrangements nicely. Several members of 

 this family are cultivated for ornament, as the hollyhock, abu- 

 tilon, hibiscus and althea. But the family is best known from 

 the cotton plant, which furnishes more material for cloth and 

 other fabrics than all other plants. The cotton fiber consists of 

 hairs which are developed on the surface of the seed ; at first they 

 are cylindrical, but on drying they become flattened and twisted, 

 so that they are easily distinguished from other fibers. There are 

 several varieties of cotton, the sea island cotton of our southern 

 states being the finest in the world. The general superiority of 

 American cotton is supposed to be largely due to climate. Cot- 

 ton grows in all tropical countries, even as far north as Tennessee 

 and Arkansas. Cotton was extensively grown and manufactured 

 in India and Egypt centuries before the Christian era. The bast 

 fibers of some of the plants of this family are valuable, and are 

 much used in China, India and New Zealand. Besides the cotton 

 fiber, the cotton seed yields an oil that from its cheapness is be- 

 ing extensively used for many purposes, adding much to the 

 value of the cotton crop. 



