ON BIASTREPSIS IN ITS RELATION TO CULTIVATION. 171 



up in the following summer which usually show but little twisting; 

 but the plants may be used as seed-bearers. The plants should 

 therefore be protected during the winter, if there is no snow, with 

 straw or leaves. A single dead leaf placed over the crown of the 

 rosette suffices to protect, if only it is kept in position, and does no 

 harm however long it remains. 



The most detailed report which I have received regarding the 

 cultivation of this breed is that of Professor Le Monnier, the Director 

 of the Botanic Garden in Nancy, who most kindly co-operated in 

 some of the experiments already described. Since 1892 he has 

 annually raised several hundred plants of my breed and cultivated 

 them under the most favourable conditions. In November of that 

 year he had 490 plants in the rosette-stage, of which 20-30 per cent, 

 showed spiral phyllotaxis and 60-65 per cent, had three-leaved 

 whorls, so that there were very few atavistic individuals. The pro- 

 portion of twisted stems agrees with my own observations (see 

 p. 160); but the number of plants with three-leaved whorls far 

 exceeds anything that I have, even now, obtained in Amsterdam. 

 Moreover, the spiral phyllotaxis appeared earlier in Nancy than in 

 Amsterdam: it was detected there in many rosettes as early as July; 

 but with me, even in early sown plants, it could never be seen before 

 August and, in the case of April or May sowings, not before Sep- 

 tember. 



Professor Le Monnier had also the goodness to repeat at Nancy 

 the experiment of sowing the seed immediately after it is ripe. This 

 was done at the beginning of September 1894: the seedlings grew 

 in the open, without any artificial heat, more rapidly and vigorously 

 than they did at the same time in Amsterdam when all possible 

 care was lavished upon them (see p. 169). Nevertheless in the follo- 

 wing year they threw up shoots which showed no trace of twisting or 

 of three-leaved whorls. At Nancy, as at Amsterdam, the production 

 of seed within a year could be induced, but at the expense of bia- 

 strepsis. 



The seed, gathered at Nancy, sown in 1897, gave in the following 

 summer only seven twisted stems and ten with three-leaved whorls, 

 out of about 100 shoots. This remarkable state of affairs must 

 probably be ascribed, as Professor Le Monnier suggests, to the 

 pollination of the twisted seedbearing plants of 1896 by pollen 

 brought by insects from other plants of Dipsacus growing at a 

 distance. This experience is the more important since I have myself 

 observed that an interval of 100 metres is often insufficient to pre- 



