SESSILE SPIKELETS IN TWO-SIDED SPIKES 37 



is always above the first glume. 

 When no glume is found below the 

 first floret, it is obvious that it is the 

 first glume which is suppressed. 



In Fig. 28 (Lepturus cylindri- 

 cus) we have a greatly thickened, 

 strongly nerved rachis with spike- 

 lets placed as in Fig. 27 but reduced 

 to the second glume and a single 

 floret. This little spikelet is sunken 

 in the hollow of the rachis joint, 

 the second glume fitting snugly 

 over the hollow, the whole forming 

 a long, slender, wiry cylinder. At 

 maturity the rachis disarticulates 

 with the spikelets firmly embedded 

 in the joints. (See diagram of 

 rachis, Fig. 28, B, and, -above, a 

 joint with spikelet removed, show- 

 ing the hollow, and a second with 

 the spikelet in position.) The plant 

 bearing these spikes grows along 

 mud flats near the sea. The rachis , 



. . FIG. 28. A, part of 



joints are cylindrical and readily spike of Lepturus 



roll down the slope to the water. %*%' B ^r 



Being corky, they are carried by 



the lightest ripples and are thus 



spread over wide areas. The grain 



germinates within its little cell, and the young roots 



and leaves push aside the water-soaked glume. 



spikelets removed; 

 above, diagram of 

 single joint. 



