Vererbung, Variation, Älutation. 257 



After reference to tlie memoirs of Winkler and Blaringhem on partlieno- 

 genesis and apogamy, the writer describes his experiments with species of Nico- 

 tiana. When certain species of Nicotiana were crossed, aborted seeds probably 

 of hybrid nature were obtained in addition to seed giving F^ plants true to the 

 maternal species. In certain other crosses the F^ contained both hybrids and purely 

 maternal plants. The latter are believed to be formed from adventitious embryos 

 arising from the nucellus. Merely tickling the capsules in several cases caused 

 slight swelling but without seed-production. Abortive seed, probably without 

 embryos, was obtained by several methods such as exposure of young plants to 

 Chloroform, or certain mutilations. Apparently seeds are never produced if pollen 

 is merely excluded from the flowers. 



The pollen grains of N, suavcolens did not germinate when placed in the 

 stigraatic fluid from iV. forgdiana, whence it is probable that an inhibitory agent 

 is present in the stigma of the latter. 



Toxic and anaesthetic gases failed to produce parthenogenesis, but when 

 young plants of N. rustica var. texana were exposed to acetone vapor the corollas 

 and stamens were transformed into leafy tissue. The injection of chemicals into 

 the Sterns of plants also failed to produce artificial parthenogenesis. 



It is concluded that the normal presence of parthenogenesis in Nicotiana is 

 very improbable, and that the seeds obtained in the crosses which come true to 

 the mother were polyembryonic and due to a Stimulus from the pollen tubes or 

 some substance exuded by them. Gates (London). 



S09) Tilmorin, P. de, Sur une race de Ble nain infixable. In: Journal 

 of Genetics, Bd. III, Nr. 1, S. 67— 76, 1 plate, 1913. 



The author obtained dwarf plants in two races of wheat; in each case the 

 dwarf character behaved as a Mendelian dominant to the tall, but it was impos- 

 sible to obtain homozygous dwarf s. All dwarf plants self-fertilized gave tall 

 plants in the ratio of about 25 to 30 percent. Experiment showed that the ab- 

 sence of homozygous dwarfs was not due to mortality after the seed was formed, 

 but since dwarf plants have rather fewer grains on the ear than tall, it is pro- 

 bable that the homozygote dwarf X dwarf, when formed, is not viable, and never 

 develops into a seed. The case is thus comparable with that of the yellow 

 mouse, in which the homozygous yellow zygote is not viable, 



Doncaster, Cambridge. 



810) Barlow, N., Preliminary Note on Heterostylism in Oxalis and 

 Lythriim. In: Journal of Genetics, Bd. III, Nr. 1, S. 53—65, 1913. 



Bateson and Gregory have shown that in Pritnula the long and short styles 

 "behave as a Mendelian pair. The author has attempted to work out the rela- 

 tions of the three types of flower — with long, mid, and short styles — in 

 Oxalis valdiviana and Lythrum salicaria. The work is complicated by the fact 

 that self-fertilizations are largely or quite sterile, and that ' illegitimate ' fertiH- 

 zations, ie. a style fertilized by pollen from a stamen of different length, are 

 also partially sterile. Thus of the 18 possible crosses, only six are fuUy fertile. 

 The work is not yet completed; the author summarizes his results as follows. 

 "(1) Reciprocals have always given like results. There is no evidence that <^ 

 and $ gamets carry different characters. (2) Long styled plants selfed give Longs 

 only. Long is pure recessive, as in Piimula. (3) There are certainly two diffe- 

 rently constituted Mid styled Oxalis, giving different ratios with the same short. 



Zentralblatt f. Zoologie, allgem. u. experim. Biologie. Bd. 3. 17 



