BIOTYPES AND HYBRIDS. 



29 



attenuate lobes, and many other variations, have behaved in many respects 

 as if they were the normal fluctuations of a single biotype. While in cer- 

 tain cases there appeared to be a marked capacity of one or the other ex- 

 treme to transmit its character to its offspring, the usual result of breeding 

 any one of these variations was a progeny giving again the whole range of 

 fluctuation, or a considerable portion of it. Time and again forms were 

 picked out so different from their sibs that they were thought to represent 

 distinct elementary species, but breeding- tests showed that their offspring 

 return completely to the usual condition of the other related families. 





Fig. 20. — Bursa bursa-fiastoris rhomboidea from a family of B. bp. simplex. 

 A half sib of the plant shown in fig. 19. 



Over 100 pedigreed families, including more than 15,500 individuals 

 derived from the two plants (040.2 and 040.7), have now been studied, and 

 of these families considerably more than half ranged between forms with 

 very obtuse lobes and others having greater or less attenuation of the lobes, 

 the extreme developments in the latter direction being scarcely distinguish- 

 able from pure-bred B. bp. tenuis; 17 of the remaining families, in which no 

 attenuate-lobed element was noted, had been injured by too long crowding 



