302 Xo)i-Isolablc Races. 



apart had 162 plants which developed stems, whilst on 

 iliat in which they were close together there were 145. 

 The ditlerence between the two reckoned as a percentage 

 of the whole culture is of course more striking, viz., 

 83% as against 20%. More important, however, is the 

 fact that per each square meter in absolute numl)ers 

 more annual individuals are produced when the plants 

 are grown far apart than when they are grown more 

 densely and therefore in larger numbers. When view^ed 

 in this way the result points to the great importance of 

 sowing seeds thinly in experimental cultures. 



Experiments with shading are met with the difficulty 

 that the young plants cannot stand it very well, even 

 when, as in my experiments, the shadow is that of trees. 

 The experiment was conducted at the same time as that 

 of 1890, referred to above, on a similar scale and by 

 growing the plants far apart; it produced about 46% 

 annuals as against 72% in the control experiment al- 

 ready mentioned. 



By far the best means, however, of increasing tlie 

 proportion of annual plants or even of securing their 

 exclusive production, is to sow the seed and keep the 

 young plants under glass. In doing so the seed can be 

 sown in March or April in un-manured sterilized soil, 

 and the seedlings may be pricked out singly into pots 

 containing richly manured soil after the appearance of 

 the third or fourth leaf. In this condition they remain 

 under glass until the end of May, at least during the 

 nights and on cloudy days, and can then be turned out 

 of the pots without breaking the ball of earth round the 

 roots and transplanted to the place where they are to 

 grow. Treate 1 in this way almost all the plants behave 



