SPI RELETS WITH HARDENED FRUITS 



77 



In all the seed-bearing spikelets so far examined, 

 the stamens and stigmas project at flowering time, 

 resulting in cross fertilization of the ovules. A few 

 grasses bear cleistogamous (close-fertilized) as well as 

 openly fertilized spikelets. 

 Such spikelets do not 

 open, and there is usually 

 but a single small stamen 

 which empties its pollen 

 directly on the short stig- 

 mas. The grain is larger 

 than that of open-fer- 

 tilized spikelets. Two of 

 our native grasses, form- 

 ing the genus Amphicar- 

 pon, related to Panicum, 

 are remarkable in that 

 they produce large cleistogamous spikelets under- 

 ground from subterranean branches (Fig. 72). The 

 plants also bear terminal panicles of ordinary and 

 much smaller spikelets, but these seldom perfect 

 seed. 



Fig. 72. Base of plant of Amphi- 

 carpon Purshii. 



SUMMARY 



In Panicese, the millet tribe, the spikelets fall 

 entire. They bear one perfect floret with a sterile 

 floret below it. The lemma and palea of the perfect 

 floret are indurate. The sterile lemma resembles the 

 second glume, the two simulating a pair of glumes, 

 while the first glume is small and looks like an addi- 



