34 Varietäten, Descendenz, Hybriden. 



tions, and these populations apparently have given a constantly 

 increasing percentage of cross-sterility. This is what should be 

 expected under the theory that a sraall difference in germ plasm 

 Constitution is active as a great difference in causing the active 

 Stimulation to pollentube growth. Breeding sister plants togetiier 

 in succeeding generations causes an automatic increase of homozy- 

 gosity as is well known. This being a fact, cross-sterility should 

 increase. Such an increase in cross-sterility has been observed in 

 the F3 and the F4 generations,. but it would not be wise to maintain 

 dogmatically that it is significant. Matouschek (Wien). 



Goodspeed, T, H., Parthenocarpy and parthenogenesis 

 in Nicotiana. (Proceed. Nation. Acad. Sciences. I. 4. p. 341—346. 

 1915.) 



The author says, that parthenocarpy is of frequent occurrence 

 in ^yNicotiana tahacum Cuba" and that parthenogenesis, employing 

 the term to mean the production of viable seed without poUination 

 (conf. Winkler in Progr, rei Bot. II. 3) is also peculiar to this 

 variety of N. tahacum. With these unusual phenomena manifesting 

 themselves during this first year of cultivation in our cultures I feel 

 that there is a possibility, at least, that after further cultivation here 

 parthenogenesis and parthenocarpy may become more nearly equal 

 in the frequency of their occurrence. The experimental results 

 above described should furnish a partial confirmation of those re- 

 ported by Thomas for her experiments on „A^. tabacum Cuba". 

 Nothing that has been said, however, must suggest that I desire to 

 confirm her general results on the basis of which she concludes 

 that parthenogenesis is peculiar to Nicotiana species in general. It 

 must, on the contrary, be emphasized that our experiments, with 

 all other species and varieties of tobacco, and those of a number of 

 other investigators, point to exactly the reverse conditions and that 

 we have no reason to suppose that parthenogenesis has ever before 

 occurred in our cultures. I have no Suggestion to offer, at the pre- 

 sent time, as to the possible origin of this A^. tabacum variety 

 which exhibits such marked divergence from the restricted method 

 of fruit and seed production peculiar to other varieties of this spe- 

 cies and to all other species of tobacco as far as known. 



Matouschek (Wien). 



Luijk, A. van, Een knopvariatie bij aardappels. [Eine 

 Knospenvariation bei Kartoffeln]. (Meded. v. h. phytopath. 

 Laborat. Willie Commelin Schölten. 1916.) 



Bei der vegetativen Linie 7 der Sorte „Zeeuwsche blauwe" fand 

 Verf. 1911 eine Pflanze, die sehr durch Mosaikkrankheit litte. Die 

 Nachkommenschaft dieser Pflanze war bis auf eine Pflanze (0712) 

 sehr stark erkrankt, und alle erkrankten Exemplaren ergaben 

 weitere Nachkommen, die auch alle erkrankten. Das Verhalten der 

 Nachkommen derjenigen Pflanzen, die eine Ausnahme, wie oben 

 gesagt, in Bezug auf die Wiederstandsfähigkeit machte, ersieht man 

 am besten aus folgender Uebersicht: 



