66 BOTANICAL GAZETTE [JANUARY 
which comes much later in the history of reduction, after the spirem has under- 
gone an enormous amount of shortening and thickening. In Oenothera it is 
a well-marked stage, immediately preceding the transverse segmentation of the 
spirem to form chromosomes; and separated from synizesis by a long interval, 
during which the spirem loosens its coils, enabling the rearrangement and thicken- 
ing of the threads to go on. 
The author’s account of the heterotypic chromosomes in O. grandiflora 
shows an evident difference between this species and the O. Lamarckiana forms. 
_ In the former, rings are said always to be produced, although no adequate evi- 
dence of their method of origin is presented. While it is probable that many 
of the rings figured are really open at one end, or with the chromosomes merely 
in contact and not fused, yet a comparison of Davis’s figs. 27-30 with my figs. 
26-34 (O. rubrinervis, 08) shows that evidently the attraction which leads a 
chromosome to pair with its mate is greater in O. grandiflora than in O. Lamarck- 
iana forms. This condition in O. Lamarckiana forms may have come about 
as a result of conditions of cultivation or hybridization, and, as I have pointed 
out elsewhere, may be directly connected with the mutation phenomena in O. 
Lamarckiana. Whether or not this is the case, I have shown that, as a result of 
this weak attraction between chromosomes, irregularities in chromosome dis-_ 
tribution during reduction actually do occur.—R. R. GATES. 
Cytology of the ascus.—BLACKMAN and Miss Fraser,™? and more recently 
Miss FRrASER"3 and Miss Wetsrorp,'4!5 have concluded that in Humari 
granulata, Ascobolus furjuraceus, and Lachnea stercorea a normal sexual process 
does not obtain. Instead of a fusion of sexual nuclei in the oogonium, a reduced 
sexual process occurs in which the female nuclei fuse in pairs with a subsequent 
asexual fusion in the asc 
Still more recently Fraser and Brooxs*® have studied further the process of 
nuclear division, methods of chromosome reduction, and spore formation in the 
above-mentioned pseudo-apogamous forms. ‘They find in each of these plants 
two sorts of reducing divisions occurring in the ascus. The first two divisions 
are heterotypic and homeotypic respectively, and thus bring about a chromosome 
reduction in the manner described for higher plants. They regard this type of 
reduction as being associated with fertilization or its equivalent. The third 
12 BLACKMAN, V. H., AND FRASER, HELEN C. I., On the sexuality and on 
of the ascocarp of Humaria granulata. Proc. Roy. Soc. London B 7'72354-38- 
™3 FRASER, HELEN C. I., On the sexuality and development of the ascocarp a 
Lachnea stercorea. Annals of Botany 21:349—-360. 1907. 
14 WetsrorD, E, J., Fertilization in Ascobolus furjuraceus. New Phytol. 7:150- 
OF. 1907. 
1s FRASER, H. C. I., AND WELSFORD, E.J., Further contributions to the cytology of 
the pods Axeate of Botany 22:465-477. 
6 Fraser, H. C. I., AND Brooks, W. E. Sr. mee studies on the cytology oF 
the ascus. Annals of Botany 23:537-549. 1909. 
