No. 529] THE NATURE OF GRAFT-HYBRIDS 



47 



of the forms which had yet been discovered. The 

 chimaera instead of being made up of two portions united 

 longitudinally was composed mainly of tissue evidently 

 of pure Solatium tiiffrum origin. A small strip, however, 

 near its base was of a different character. This region 

 consisted of a single leaf, and a small amount of tissue 

 lying below belonging to the stem. The same form was 

 secured a second time where it developed from a five- 

 fold chimaera derived from 8. proteus. Unfortunately, 

 it was not possible to propagate this second specimen. 



In order to isolate this new form it was necessary to 

 cause the axillary hud belonging to the single leaf to 

 develop into a shoot. This was finally successful after 

 four decapitations of the Solatium til g rum shoot above 

 it. The final result was a branch which was very dif- 

 ferent from any of the previously developed forms and 

 it was named Solatium daririuianum. The point of spe- 

 cial interest in connection with this form is that of all 

 graft-hybrids which Winkler secured, this seems to be 

 the only one which is likely to prove a hybrid in the 

 strict sense of the word. This point, however, will be 

 brought out later in the discussion of the real nature of 

 these graft-hybrids. 



All of the hybrids were propagated further by cut- 

 tings and with the single exception of Solanum koel- 

 rcutcriatium, were made to produce ripe fruit which in 

 all cases was more or less intermediate in character be- 

 tween the fruit of the nightshade and the tomato. In 

 Solatium darwinianum, however, the fruit was all sterile 

 and no perfect seeds were formed. The fruit itself is a 

 small round berry like the fruit of the nightshade in 

 form, but having the color and structure of the tomato. 

 In Solanum koelreuterianum the young fruit set but 

 failed to reach maturity. 



Of the hybrids Solatium tubingense is the most fertile 

 and produces fruit very abundantly. A considerable 

 number of the fruits, however, are sterile or "partheno- 

 carpic" and the seeds in no cases reach their full de- 



