FLOWERS, FRUITS, AND SEEDS 



365 



[Chap. XXXII 



tain from one to many ovules or seeds, but usually only one of the two 

 ovules in a fruit of peach becomes a seed. Another significant similarity 

 in these two fruits is the two obvious layers of tissue in tlie carpel. The 

 inner of these two layers in the peach ripens dry and stony, whereas 

 the outer layer ripens soft and juicy. In the bean pod both of these 

 layers ripen dry and hard. The fruit of grape is a third type of simple 

 fruit in which the whole ovulary ripens soft and juicy. 



The peach is an example of stone fruits, or drupes. Other examples of 

 stone fruits are plum, cherry, olive, apricot, mango, almond, and the 

 fruits of hackberry, poison ivy, basswood, and American holly. The 

 suture formed by the fusion of the margins of the single carpel of these 

 drupes is usually evident as a slight groove on one side of the fruit. The 

 almond differs from the other fruits in the list in that the entire fruit 

 becomes dry at maturity. The coconut likewise resembles a stone fruit, 

 but it consists of three carpels, both layers of which ripen dry and hard. 



The grape exemplifies the berry type of fruit. Other examples are 

 persimmon, date, avocado, nightshade, lemon, orange, grapefruit, and 

 tomato. 



Simple dry fruits may be one-seeded and indehiscent, as the akene of 

 buckwheat, and the grain, or caryopsis, of wheat, corn, and other grasses. 

 They are said to be indehiscent because they do not split open when 

 mature. In all grains the ovulary wall is united with the coats of the single 



Fig. 162. Several types of simple fruits: A, maple; B, elm; C, ash; D, basswood; 

 E, dandelion; F, sunflower; G, clematis. 



seed. The shelled nuts of hickory, pecan, walnut, oak (acorn), and chest- 

 nut as they appear on the market are similar to akenes. The individual 

 fruits of sunflower, dandelion, and other plants of the composite family 

 are also called akenes, but they are not simple fruits, for they consist of 

 an ovulary united with a floral cup (Fig. 162). The winged fruits of 

 maple, ash, and elm are similar to akenes. 



