220 



OUTLINES OF PLANT LIFE. 



or even juicy. In accordance with these differences, two sorts 

 of fruits are recognized, namely, dry fruits and fleshy fruits. 

 Between these, however, there is no sharp line of demarca- 

 tion. 



307. Dry fruits. — If the pistil contain only one or two 

 seeds, it very often does not open at maturity. Consequently, 

 the seed-coats ordinarily remain thin, and the protective 

 function is put upon the pericarp. In some cases the carpels 

 become adherent at an early stage to the surface of the ovyle, 



123^ 5 



Fig. i87.-7_A small portion from the margin of a transverse section of grain of oats, 

 1, 2, pericarp; 3, seed-coats; 4, remains of the sporangium; 5-7, endosperm; 5, 

 gluten cells; 6, cells containing large compound starch-grains (compare fig. 114) at 

 7, richer in gluten, with less starch. Magnified about 325 diam,— After Harz. 



and at maturity the pericarp is so firmly attached that it can 

 scarcely be distinguished from the seed-coats themselves. 

 Such a change takes place in the fruit of most grasses, and the 

 grain so formed is ordinarily mistaken for a seed (fig. 187). 

 When dry fruits are one-seeded and indehiscent the pericarp 

 usually bears whatever special contrivances are necessary for 

 the distribution of the seeds. (See further ^f 395 if.) If, 

 however, the pericarp contains many seeds, it generally breaks 

 at maturity to allow the loosene4 seeds to escape. The ex- 

 tent and position of the opening into the seed chamber or 



