30 BURSA BURSA-PASTORIS AND BURSA-HEEGERI : 



in the seed-pans. This cause, with the ravages of thrips, in many cases 

 so affected the development of the plants during several months of the 

 summer of 1906 that it was often very doubtful just how much depend- 

 ence was to be placed upon the observed results. However, enough of 

 tlie families developed healthily to render it not improbable that all degrees 

 of variation between completely unlobed individuals and those with highly 

 developed attenuate lobes may be normal fluctuations of a single unit-form. 



Of the healthy cultures several may be taken as examples of the pecu- 

 liar behavior of these plants. Several noteworthy instances were presented 

 in which the conditions of the parent were transmitted to the offspring 

 with only a narrow range of fluctuation. Thus, in the second of the two 

 original families from which all of these variable cultures sprang, there 

 were among- 70 specimens 13 which had attenuate lobes. Seeds of 1 of 

 these attenuate-lobed specimens (057.20) were sown October 9, 1905, and 

 produced 681 plants, all but 1 of which showed almost uniformly strong 

 development of attenuate lobes. One specimen was entirely free from 

 lobation of any kind, but it produced no good seeds and therefore it was 

 impossible to test the significance of this unlobed condition. One of the 

 attenuate-lobed plants of this family (0520.196) produced 35 more or less 

 attenuate-lobed offspring, and some which were unlobed, but the latter 

 were so crowded in the seed-pan that stunting might be considered the 

 cause of the suppression of attenuate lobes. Progenies of 4 of these 

 stunted individuals (05196.134, 05196.136, 05196.137, and 05196.147) have 

 since been examined. Two of these 4 families (06136 and 06137) had 

 the wide range of variation usually found in the related families, and the 

 other 2 (06134 and 06147) contained unlobed or slightly obtuse-lobed 

 specimens. Since these last 2 families were badly crowded, little de- 

 pendence is to be placed upon this behavior. 



Leaving out of account all the families which may have been injured by 

 crowding or otherwise, in 3 other instances the offspring were uniform 

 and in fair agreement with the parent. All 3 of these belonged to the 

 first of the 2 original families. Seeds of a well-developed obtuse-lobed 

 individual (052.24) sown January 16, 1906, produced 100 specimens 

 of uniform aspect, with only well-developed obtuse lobes. An obtuse- 

 lobed sib of the last (052.179) was the parent of 130 plants of the same 

 uniform character, having well-marked sinuses, but acutish, not elongated 

 lobes. One of these (05179.170) produced about 30 obtuse-lobed offspring, 

 but thrips injured them so much that their characterization was unsafe. 

 Another obtuse-lobed plant (052.193), a sib of 052.24 and 052.179 just 

 described, gave a progeny of 125 plants of very uniform aspect throughout 

 and always with well-developed sinuses and obtuse lobes. 



In all these exceptional cases there seems to be a consistent behavior 

 in that the parental character dominates the entire progeny, but in each 



