212 



PLAXT STRUCTURES 



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 Composite, 

 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. 186, 187), or by animals 

 (Fig. 188). 



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 or- 

 ganizes two layers, the inner being 

 very hard, forming the " stone," the 

 outer being pulpy (Fig. 189), or vari- 

 ously modified (Fig. 190). 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 ferti- 

 lization in chang- 

 ing structure is 

 felt beyond the 

 ovary. In the ap- 

 ple, pear, quince, 

 and such fruits, 

 the pulpy part is 

 the modifie d 



Calyx (one Of the FIQ. 1S6. Winged fruit of maple. After RERNI;R, 



FIG. 1&5. A pod of fireweed 

 (Epilobium) opening and 

 exposing its plumed seeds 

 which are transported by 

 the wind. After BKAL. 



