Februasy 25, 1916] 



SCIENCE 



291 



tains. In general there is good evidence from the 

 standpoints of extreme variability and correlated 

 gametic sterility of the widespread occurrence of 

 natural hybridism in the genus Bubits. The 

 genus accordingly affords one more argument in 

 favor of the view now rapidly gaining ground, 

 that hybridism is at once a prominent cause of 

 variability and the appearance of new species in 

 the Angiosperms. 



Pollen Sterility in Relation to the Geographical 

 Bistriiution of Some Onagraoece: Cakl C. 

 FORSAITH. (Presented by E. C. Jeitrey.) 

 The genus CEnothera has been mentioned fre- 

 quently in communications concerning mutation 

 and hybridization. It seems fitting, therefore, 

 that other genera of the Onagracefe should be ex- 

 amined for evidences of inter-species crossing. 

 The well-established correlation of pollen sterility 

 and hybridization is considered as a determining 

 factor in this connection. Studies of the Chamae- 

 nerion subgenus of Epilobium presents interesting 

 results. Anthers chosen from the more southern 

 representatives of Epiloiium angustifolium L. 

 show uniformly potent microspores. Selections of 

 material from stations where this plant is coexist- 

 ent with its ally, E. latifolium L., disclose often 

 abundant abortive pollen grains. The more uni- 

 formly distributed group belonging to subgenus 

 Lysimachion, reveals impotent microspores quite 

 generally. The monotypio Zauschneria calif ornioa 

 Presl. and the geographically limited Epiloiium 

 angustifolium, are seen to present unimpaired fer- 

 tility. E. angustifolium, however, occurring 

 within the territorial limits of E. latifolium in 

 North America, manifests microscopic proof of 

 previous cross-fertilization. This feature is in 

 marked contrast to the more uniformly perfect 

 pollen development habitually present in the geo- 

 graphically limited species just mentioned. Thus 

 it is apparent, from the morphological standpoint, 

 that interspecies crossing is a not uncommon oc- 

 currence among the Onagraceffi where such is not 

 prevented by kinship or distribution. This inter- 

 esting fact was first noted by Miss Enth Holden, 

 of Cambridge, England. 



Seed Sterility and Delayed Germination in CEno- 

 thera: B. M. Davis. 



A study of fifty species, races and hybrids of 

 CEnothera, have given surprising data on the ex- 

 tent of seed sterility and delayed germination 

 within this group. The importance of recognizing 

 in genetical work the problems presented by this 

 situation will be discussed and illustrated. A 



method will be outlined whereby it is hoped that 

 complete germination of seeds may be rapidly 

 forced to completion and at the same time may 

 permit of the preservation for examination of the 

 residue of sterile seed-like structures. 

 The Production of lJt{-^) -Chromosome Mutants 



by llt-Chromosome CEnothera LamarcTciana: 



Anne M. Lutz. 



Gates and Thomas have counted 15 chromo- 

 somes in 21 plants variously classified as CEnothera 

 mut. lata, 0. mut. semilata, 0. lata to semilata, 

 0. mut. lata rubricalyx, 0. biennis mut. lata and 

 as lata-Wke forms. Gates had mentioned these re- 

 sults in an earlier paper in 1913 referring 

 to 0. mut. lata rubricalyx, which was found among 

 the F: offspring of a cross between two 14-chromo- 

 some forms, he says : ' ' The possession of fifteen 

 chromosomes by this plant also shows that when- 

 ever a meiotio irregularity leads to the formation 

 of an individual having an extra chromosome, 

 such a plant will have the leaves and habit of 

 lata or semilata." Although he adds in a foot- 

 note that "it is possible that one or two other 

 mutants also have an extra chromosome," he does 

 not state that such forms are not Zata-like; 

 furthermore. Gates and Thomas say later ' ' Cer- 

 tain other mutants indicate by their hereditary 

 behavior that they may also have aberrant chromo- 

 some numbers, but this has not yet been proved, 

 except in gigas." All of the arguments offered 

 by Gates and Thomas point to the conclusion that 

 whenever a meiotic irregularity in a 14-chromo- 

 some form leads to the production of an 8-chromo- 

 Eome gamete, if the latter is capable of function- 

 ing, the union of this cell with a 7-chromosome 

 cell will produce 0. lata, 0. semilata, or some lata- 

 like form. While many 15-chromosome forms have 

 lata or lata-lite characters, many 15-chromosome 

 mutants, offspring of 14-chromosome forms, are 

 quite unlike 0. lata. I have counted 15 chromo- 

 somes in 11 distinct mutant types: (1) 0. lata, 

 (2) 0. albida, (3) 0. bipartita, (4) type 5,509, 

 supposed to be a modified form of de Vries's ob- 

 longa, (5) 0. nanella lata, (6) 0. subovata, (7) 

 type 2,256, (8) type 4,499, (9) 0. exilis, (10) 0. 

 exundans, (11) type 5,365. The first six are pro- 

 duced by 0. LamarcTciana and other forms — the 

 first four being very common types. Type 2,256 

 is produced by 14-chromosome 0. nanella, selfed, 

 type 4,499 by 0. lata, selfed, and by 0. lata X 0. 

 Lamarolciana, while the three remaining mutant 

 types have been observed in cultures of selfed 

 lata only, thus far. In addition to the foregoing. 



