H. M. Leakb 233 



It is clear that this system of record, though the best that has been 

 devised, is subject to considerable disadvantage. It is, at the best, 

 approximate and moreover the determination is only possible when the 

 main stem has received no check to growth. In practice this continued 

 growth of the main stem is rendered a fact of comparatively infrequent 

 occurrence from the climatic conditions prevalent at the early stages of 

 growth. These conditions favour insect life of all kinds and the larval 

 stage of Earias sp. is commonly met with on the cotton plants. This 

 pest penetrates the young stem at the leaf axil and from this point 

 bores its way downwards. The stem so attacked withers and growth is 

 continued by an enhanced development of the secondary branches. In 

 such cases it becomes difficult and frequently impossible to determine 

 this character even approximately. 



The length of the vegetative period is most readily expressed in the 

 number of days from the date of sowing to the appearance of the first 

 flower. Unlike the previous character this lends itself to accurate 

 record. The fields are visited daily and the plants in flower for the 

 first time noted. Yet numerous subsidiary influences are here found to 

 aflfect the date of production of the first flower and render the figure, 

 though accurate in itself, only approximately accurate as an indication 

 of a definite individual character. The more important of these 

 influences may be here referred to. 



In the first place, there has been found a considerable seasonal 

 variation ; that is, a considerable difi"erence in the length of the 

 vegetative period of a pure type from one year to another. Hence 

 the figures obtained for one year only are strictly comparable and it 

 is possible to compare the results of two or more years by introducing 

 a seasonal factor by the addition (or subtraction) of which the results 

 of any two years are rendered comparable. This is illustrated in the 

 column of Table XV for the years 1907 and 1908. 



In the second place the length of the vegetative period is materially 

 influenced by the method of cultivation. Two methods have been 

 employed in the course of these experiments. In the first the seed is 

 sown in pots and the young plants, when a month to six weeks old, 

 planted out. In the second the seed is sown in the ground about 

 a month after the sowings in pots have been eflfected. Here only 

 indirect comparison is possible and the efifect of such variation in the 

 method of cultivation is shown by a comparison between the third and 

 the first two columns of Table XV. 



Unfortunately no records are available by which the direct influence 



