28o 



" Couch " or " Twitch." 



[JULY, 



or broadest face is next the axis, whereas in the ears of 

 perennial rye-grass, which those of couch resemble super- 

 ficially, the spikelets are arranged with the narrow, rounded 

 face towards the axis of the ear. In some forms of the plant 

 the glumes have short beards or awns. 



The pest is propagated in two ways, namely, by seeds and 

 by the underground rhizomes. Ordinarily the plants have not 

 much opportunity to flower among farm crops, but flowering 

 specimens are commonly seen in July and August in the 

 hedgerows. The seeds ripen a little later and are blown on to 

 the land, where they germinate and produce a new crop of 

 weeds. Sometimes the seeds are introduced in unclean 

 samples of grass and seed-oats. Although more couch plants 

 arise from seeds than is generally supposed, the chief mode 

 of propagation is by means of the creeping underground 

 stems. These spread through the soil and soon form a dense 

 mat of couch, which it is difficult to remove. In addition to 

 natural extension from one point of the soil to another, the 

 plant is inadvertently spread by the farmer during the cul- 

 tivation of the land. The rhizomes get broken or cut up into 

 short lengths by ploughs, hoes, and cultivators, and are moved 

 about in the soil by these implements. Each small piece on 

 which there is a single joint or node has its bud and set of 

 adventitious roots, and is virtually a complete plant capable 

 of extensive growth. It will be readily understood that a 

 single couch plant may become broken up into a large number 

 of such growing pieces and soon cover a wide area of ground. 



Black "Twitch" or Common Bent. — This has a creeping 

 habit, but its stems lie on the surface of the soil, and do 

 not creep below like those of true couch. In some dis- 

 tricts this is far the more prevalent kind of twitch, true 

 couch being comparatively rare. The leaves are short and 

 flat, and dull green ; in some forms smooth, in others rather 

 rough. The inflorescence is a panicle with fine slender 

 spreading branches and purplish-green one-flowered spikelets 

 of very small size (Fig. 3). There are no auricles at the 

 base of the leaf-blade, but there is a membranous structure 

 — the ligule — where the blade and sheath join. In true couch 

 the ligule is absent or extremely short. These differences 

 serve to distinguish black twitch from true couch when the 

 plants are not in flower. 



