FRUITS AND SEEDS 



191 



hairs. The awn is hygroscopic, winding up in dry 

 weather, and uncoiling in damp. When it falls to the 

 ground, the fruit may be blown along by the wind, or, 

 if the wind is insufficient to move it, it will slowly crawl 

 about by the winding and unwinding of the awn. On 

 reaching a soft spot, the movements of the awn will force 

 the pointed end of the mericarp into the soil ; here it is 

 anchored fast by the reflexed bristles which cover its 

 beak. 



In the Umbelliferae the schizocarp, which is inferior, 

 splits into two one-seeded portions (Fig. 96). In the 

 mallow (Fig. 97) and hollyhock the ovary is superior and 



FIG. 94. DOUBLE SAMARA FIG. 95. SCHIZOCARP or STORK'S-BILL 



OF SYCAMORE. (Erodium ),SHO WING MERICARPS SPLIT- 



TING AWAY FROM CENTRAL PlLLAR. 



a, persistent calyx. To the right a 

 completely detached mericarp. 



multilocular, and separates into numerous achenial 

 sections. In the Labiatse the fruit consists of four nutlets 

 derived from a two-carpelled ovary. This ovary was 

 originally two-chambered, with two seeds in each chamber, 

 but by the ingrowth of the wall, four chambers are formed, 

 each containing one seed. The chambers then separate, 

 and we get four little nuts. 



Generally speaking, we may say that in a dry syn- 

 carpous fruit, if each chamber contains but one seed, 

 the carpels separate into one-seeded indehiscent portions ; 

 if many seeds are present, each chamber splits open to 

 allow for the escape of the seeds, and we get a capsule. 

 It is simply a question of biological convenience. 



