30 THE TRUE GRASSES. 



has a support (a neighboring culm or merely an un- 

 evenuess in the soil). This rotation and nutation, to- 

 gether with the action of the bristles, soon causes the 

 bract surrounding the fruit to bore deeply into the 

 ground (observed in several Stipa species, Heteropogon 

 contortus R.. & Sch., Avenafatua L. and A. barbata Brot, 

 several Aristida species from Brazil and New Holland). 

 If such boring fruits get into the wool of sheep, many 

 kinds will in a short time bore through the skin into 

 the intestines, where they cause fatal inflammation (ob- 

 served in Stipa capillata L. in Russia, St. spartea Trin. 

 in N. America, Aristida hygrometrica Br. in Queensland, 

 Heteropogon contortus R. & Sch. in New Caledonia). Fruit 

 may also bury itself without the help of twisted awns ; in 

 Triticum ovatum Godr. the spike falls off entire, and since 

 it possesses a very pointed base and numerous outward- 

 pointing rough aw r ns, wherever these find a hold they exert, 

 by every movement of the wind, etc., a pressure upon the 

 point, and this drives it into the ground. (Herbarium 

 specimens loose between papers, creep backwards of 

 themselves.) The entire inflorescence of Cornucopice 

 (Fig. 46) falls off at the time of fruit, and the stem then 

 becomes curved and very pointed at the end. Whether 

 this serves to bury it or to attach it to animals is un- 

 certain. 



The awns of Avena sterilis L. have a peculiar use. 

 Two strongly awned fruit-bracts fall off fastened to- 

 gether ; in moist surroundings the twisted awns begin 

 to rotate their diverging upper halves, consequently they 

 cross and press against each other until the bracts are 

 forcibly separated, thus giving the fruit an impetus 

 which throws it for some distance. 



Finally, we will mention a peculiar method of dis- 

 tribution, viz., distribution by means of leafy spikelets. 

 In many grasses, especially in high latitudes (south as 

 well as north) and upon high mountains where the 

 ripening of the fruit is often uncertain, it is not rare that 

 entire spikelets or single flowers with floral glume and 

 palea transform themselves into small-leaved shoots 

 which are provided at the base with the beginnings of 



