SPERMATOPHYTES : ANGIOSPEKMS 



371 



The testa is variously developed in seeds, sometimes 

 being smooth and glistening, sometimes pitted, sometimes 

 rough with warts or ridges. Sometimes prominent append- 

 ages are produced which assist in seed-dispersal, as the 

 wings in Catalpa or Bignonia (Fig. 115), or the tufts of 

 hair on the seeds of mi]kweed, cotton, or fireweed. 



216. The fruit— The effect of fertilization is felt beyond 

 the boundaries of the ovule, which forms the seed. The 

 ovary is also involved, and becomes more or less modified. 

 It enlarges more or less, sometimes becoming remarkably 

 enlarged. It also changes in structure, often becoming 

 hard or parchment-like. In case it contains several or 

 numerous seeds, it is organized to open in some way and 

 discharge them, as in the ordinary i^ocls and capsules (Fig. 

 122). In case there is but one seed, the modified ovary 

 wall may invest it as closely as another integument, and a 

 seed-like fruit is the result — a fruit which never opens and 

 is practically a seed. Such a fruit is known as an akene^ 

 and is very characteristic of the greatest Angiosperm family, 

 the Compositae, to which sunflowers, asters, golden-rods, 

 daisies, thistles, dandelions, etc., belong. Dry fruits which 

 do not open to discharge the seed often bear appendages 

 to aid in dispersal by wind (Figs. 116, 117), or by animals 

 (Fig. 129). 



Capsules, pods, and akenes are said to be dry fruits, but 

 in many cases fruits ripen fleshy. In the peach, plum, 

 cherry, and all ordinary " stone fruits," the modified ovary 

 wall organizes two layers, the inner being very hard, form- 

 ing the "stone," the outer being pulpy, or variously modi- 

 fied (Fig. 330). In the true berries, as the grape, currant, 

 tomato, etc., the whole ovary becomes a thin-skinned pulpy 

 mass in which the seeds are imbedded. 



In some cases the effect of fertilization in changing 

 structure is felt beyond the ovary. In the apple, pear, 

 quince, and such fruits, the pulpy part is the modified 

 calyx (one of the floral leaves), the ovary and its contained 



