168 ON BIASTREPSIS IN ITS RELATION TO CULTIVATION. 



to be most suitable, I made use of a large shallow water-bath, 10 cm. 

 in thickness, which occupied a closed space in the small greenhouse 

 attached to my laboratory and was distant only 20-25 cm. from 

 the glass above it, being inclined so as to be about parallel to it. 

 The pots were 10 cm. in diameter; each either contained a single 

 plant from the beginning or two plants, the weaker of which was 

 removed so soon as they began to touch each other. By a control- 

 experiment it was ascertained that it would not suffice to heat the 

 water-bath only during the day-time; plants treated in this way 

 threw up no shoots in the following summer. Continuous heating 

 was required, and this was carried on from the middle of September, 

 when the sowing took place, until the middle of November, at which 

 time the seedlings had five or six pairs of leaves, the leaves being 

 about 14 cm. in length. 



The experiments were begun on September 17, 1892, and on 

 September 15, 1893, the seed used being in each case that which had 

 just before been harvested. With the success of the experiments the 

 whole life-cycle of these biennial plants was brought within the 

 limits of a single year; and it would eventually become possible 

 thus artificially to grow them as annuals and perhaps in time to 

 establish an annual variety by selection. 



Sowing of September 17, 1892. The seed was harvested and sown 

 on the same day: it was obtained from a plant the seeds of which 

 gave 20 per cent, of twisted stems when cultivated in the ordinary 

 way. Germination and the early stages of growth were quickly and 

 satisfactorily gone through. Tne water-bath was heated until the 

 middle of November; subsequently only the greenhouse was heated. 

 At the end of January 1893 the plants were put out into a cold 

 frame, where they proceeded to form new leaves, those which had 

 been formed in the greenhouse now dying off. In the middle of 

 March they were planted out, and after the middle of April they 

 were no longer protected by glass. 



At the beginning of June there were nineteen plants with vigorous 

 shoots 50-75 cm. in height and twenty-two rosettes. At the end of 

 June the nineteen shoots were nearly two metres in height and 

 were as vigorous as average plants of my breed. The examination 

 of these shoots showed (1) that eight of the plants had normal 

 decussate phyllotaxis; (2) that there were seven plants which, 

 although their phyllotaxis was decussate, had each a four-leaved 

 whorl owing to the suppression of an internode; (3) that there were 

 four plants with slight and local twisting in the shoots which were 



