ioo8 
Gates. — Somatic Mitoses in Oenothera . 
Finally, two cases were observed in which the spindles were exception- 
ally large and the chromosomes were many of them closely joined in pairs 
to form bivalents, though retaining the shape of the somatic chromosomes. 
These bivalents were peculiarly oriented on the spindle, and from all analogy 
it seems very probable that this pairing would be followed by an actual 
reduction division in somatic tissue. 
In conclusion, I am greatly indebted to Professor J. Bretland Farmer, 
F.R.S., for suggestions and criticisms in connexion with this work. 
Note added Aug. 29.— -In a paper which has just appeared (‘Triploid 
Mutants in Oenothera / Biolog. Centralbl., 1912) Miss Lutz affirms the 
incorrectness of certain of her earlier counts of 14 chromosomes for O. lata, 
and finds 15 chromosomes in the root tips of all the lata plants she has 
examined. In a re-examination of the preparations of O. lata (now some- 
what deteriorated) described in my first paper on the subject (‘ Pollen 
Development in Hybrids of O. lata and O. Lamarckiana , and its Relation to 
Mutation/ Bot. Gaz., Feb., 1907) I was unable to determine with certainty 
whether this lata plant contained 14 or 15 chromosomes. But from all the 
evidence now at hand, it is safe to conclude that O. lata nearly always con- 
tains 15 chromosomes, though it is quite possible there may be exceptions 
in the case of certain forms of lata which produce plenty of pollen. It is 
probable that the almost complete sterility of the pollen in typical lata is 
concerned with the presence of the extra, unpaired chromosome. 
Literature cited. 
Boveri, Th. (’ 09) : Die Blastomerenkerne von Ascaris megalocephala unddie Theorie der Chromo- 
somenindividualitat. Arch. f. Zellforsch., iii, 181-268, Pis. VII-XI. 
Farmer, J. B., and Shove, Dorothy (’05): On the Structure and Development of the Somatic 
and Heterotype Chromosomes of Tradescantia virginica. Quart. Journ. Micr. Sci., xlviii, 
559-69, Pis. XLII-XLIII. 
Gates, R. R. (’07) : Hybridization and Germ-cells of Oenothera Mutants. Bot. Gaz., xliv, r-21. 
(’08) : A Study of Reduction in Oenothera rubrinervis. Bot. Gaz., xlvi, 1-34, 
Pis. I-III. 
(’11a) • The Mode of Chromosome Reduction. Bot. Gaz., li, 321-44. 
* (’ll b ) : PollenTormation in Oenothera gigas. Ann. of Bot., xxv, 909-40, Pis. 
LXVII-LXX. 
Kemp, H. P. (TO) : On the Question of the Occurrence of £ Heterotypical Reduction ’ in Somatic 
Cells. Ann. of Bot., xxiv, 775-803, Pis. LXVI-LXVII. 
Lillie, F. R. (’09) : Polarity and Bilaterality of the Annelid Egg. Experiments with Centrifugal 
Force. Biol. Bull., xvi, 54-79, Figs. 9. 
Lutz, Ann M. (’09) : Hybrid Oenotherae. Notes on the First Generation Hybrid of Oenothera 
lata ? x O. gigas <J. Science, N.S., xxix, 263-7. 
Nemec, B. (TO) : Das Problem der Befruchtungsvorgange und andere zytologische Fragen. Berlin, 
PP- 53 2 , Pis- 5> Figs- IT 9* 
