160 Some Factor's in Plant Comj^etition 



The crowding, therefore, was very disadvantageous to the production 

 of ears, and the paucity of fruiting stems in the inner parts of the 

 square supports the idea that overcrowding in the field may have a very 

 definite tendency to reduce the crop by weakening the plants below fruit 

 bearing standard. 



2. Number of tillers per plant. Apart from the ears produced the 

 number of tillers thrown out by each plant is instructive. 62 out of 64 

 spaced plants had from 8-20 tillers and of these more than half pos- 

 sessed from 10-12 stalks, no plants showing less than 8. Over- 

 crowding, however, tended both to decrease and increase the number of 

 stalks, widening the range of variability in this respect. This suggests 

 that when no competition for light occurred the plants tended towards 

 the production of a standard number of stalks, whereas when com- 

 petition was very keen each plant, in playing for its own hand, produced 

 a number of stalks in accordance with the particular advantage or 

 disadvantage it gained. (Fig. 7.) 



With the spaced plants the position in the greenhouse had" no bearing 

 on the tillering, but in the crowded square the outside rank carried the 

 largest number of stalks per plant, the second rank came a bad second, 

 while the two innermost squares bore the smallest numbers of tillers, 

 which were of a weakly character. In this respect the amount of tillering 

 and ear formation ran parallel. (Fig. 8.) 



Where the plants had sufficient space some correlation occurred 

 between the number of tillers produced and the number of ears formed, 

 but when they were crowded this correlation disappeared. In the 

 spaced plants nearly all the plants with ears had 8-18 stalks, while 

 the largest number of the standard 6-8 ears (see p, 158) were produced 

 on plants with 10-14 stalks, very few being outside this limit, thus 

 roughly speaking every other tiller bore an ear. Among the crowded 

 plants most of those with 4-12 tillers bore no ears at all, the ears being 

 usually produced by plants with 14-26 stalks, but no regular increase 

 in the number of ears occurred with increased tillering. Adequate 

 spacing, therefore, tends to reduce the number of tillers per plant that 

 are necessary to produce a certain number of ears, and also causes a 

 tendency towards a certain standard plant in which the number of 

 tillers and ears formed vary within rather narrow limits. With over- 

 crowding this standard plant disappears, and the amount of tillering 

 gives no index of the number of associated ears. 



3. Compdrative dri/ ircKjlits of jjlanls. The dry weights of the barley 

 plants bore out the observations that adequate spacing tends to the 

 production of a more even type of plant, while crowding accentuates 



