50 GRASSES OF lO^WA. 



and spike-like, as in timothy or in meadow foxtail. All gra- 

 dations of form between these two extremes occur. 



Pollination and fertilization. — Grasses are mostly anaemophi- 

 lous, that is, pollinated by tbe wind. Fiowers, as stated above, 

 are mostly hermaphrodite; some are mon ecious and a few 

 dioecious. In monoecious grasses like Zea the staminate 

 tlowers form the so-called tassel. Each staminate flower con- 

 tains three stamens; whea mature they hang loosely from the 

 llower. The pollen consists of small round grains easily 

 shaken out of he versatile anthers. The slightest breeze suf- 

 fices to set the anthers in motion, causing them to shed "loads 

 of pol'en. " Since the pollen is light it may be easily carried 

 by the wind. The pistillate flowers occur in the axils of the 

 leaves and constitute the so-calh d cob. Each ovule has com- 

 ing from it a long, slender filiform thread, the stigma, provided 

 with plumose hairs. These p umose bairs are readily made 

 out with the naked eye and are for the purpose of holding the 

 pollen grains. The moist surface of the stigma causes the 

 pollen grain to germinate. It sends a slend r tube down the 

 syle to the ovule where the genera ive nucleus unites with the 

 egg cell of the ovule, and asartsult( f this fertilization the kernel 

 develc ps into a seed. Corn produces an erormous amount of 

 pollen. Much of this is of course wasted. The staminate 

 flowers are visited by honey bees and other insects chiefly for 

 the pollen. Corn, when ia flower, has a decided odor. 



Bulbilis clactyloides is said to be dioecious. Mr. Plank* made 

 some observations which led him t > believe that the grass was 

 not dioec'ous but monoecit us, and Professor Hitchcock, f in 

 order to verify ihis statement, conducted tbe following experi- 

 ments. A few seeds of the spec es were germinated. A sin- 

 gle stolon was transferred to an out-door plat. This produced 

 numerous stolons gradually spreading over the ground. The 

 second season witnessed no flowers, but the third season both 

 staminate and pistillate fl wers were produced, the staminate 

 preponderating. The flowers made their appearance mostly 

 at the nodes, so that in reality they started as independent 

 plants. 



In Distichlis spicata and occasionally Poa arachnifera the 

 plants are dioecious. In the^e cases the pollen must come 

 from other plants. 



*Buchl()e dactyloides Eaglm. not a dioecious grass. Bui. Torr. 19: 303. 1893. 

 +Note on buffalo grass. Bot. Gazette. 20: 464. 



