152 BOTANICAL GAZETTE [FEBRUARY 
nothing which demands any fundamental revision of his theories in regard 
to the réle of the nucleus in heredity. 
Soon after this paper by STRASBURGER appeared, WINKLER” published a 
description of the generation obtained from the seed of his graft hybrids, and 
includes an account of the chromosome numbers. In Solanum Lycopersicum 
the x and 2x numbers are 12 and 24; while in S. nigrum they are 36 and (prob- 
ably) 72. He suggests that the difference ip chromosome numbers may pre- 
vent the crossing of these two species, although he recalls that ROSENBERG 
crossed two species of Drosera with 10 and 20 chromosomes in their x genera- 
tion, and obtained a hybrid with 30 chromosomes as the 2x number. If the 
Solanum graft hybrids are due to a fusion of somatic nuclei, they should have 
72+24, or 96 chromosomes, unless the fusion should be followed by a regu- 
lative reduction, in which case the number should be 48. WINKLER found 
the « number to be 36 in Solanum tubingense, S. Darwinianum, and S. Gaert- 
nerianum, and found 12 in S. proteus and in S. Koelreuierianum, the first three 
of these, in their pollen formation, reverting to S. nigrum, and the other two 
reverting to S. Lycopersicum. The sterility of S. Koelreuterianum and S. 
Darwinianum might be due to a difference in chromosome numbers of micro- 
spores and megaspores. The microspore number is 12, but the megaspore 
number remains to be determined. In all five of the graft hybrids the develop- 
ment of the pollen is regular, but it is still to be determined whether the germ 
cells are pure or hybrid. WHuNKLER thinks it is more reasonable to suppose that 
the graft hybrids more closely resembling S. nigrum are from S. nigrum cells, 
and that those resembling S. Lycopersicum are from cells of that parent, the 
nuclei being those of one parent or the other, but the cytoplasm being mingled 
with that of neighboring cells. If such cytoplasm should have so great an 
influence, it would interfere with the theory that the nucleus is the sole bearer 
of oo characters. 
In an addendum to this paper WINKLER severely criticizes STRASBURGER 
for publishing anything before the cytological details had been made public. 
TRASBURGER certainly would not have taken part in the matter had it not been 
that his cytological theories had been attacked. Had some cytological evi- 
dence accompanied WINKLER’S attack upon theories which STRASBURGER has 
held and defended almost for a Lobe ined unpleasantness could have been 
avoided. In this addendum WinKLEeR that in September 1907, at the 
Dresden meeting of the Deutsche hohe Geslchft he had suggested that 
the Solanum graft hybrids might be complicated chimeras, a sort of mosaic 
of the two parents. This suggestion seems oto are reviewer to be a good work- 
_ ing hypothesis, and if the suggestion is really a fact, an intensive study of the 
nuclei and cytoplasm of the graft might enable one to recognize, even in 
vegetative tissues, just what cells have been derived from each parent, while 
in the reduction divisions the recognition should not be difficult. 
™ WINKLER, Hans, Ueber die Nachkommenschaft der Silanes Pee 
und die Chrcindadtasaisaliien ihrer Keimzellen. Zeitschr. Bot. 2:1-38. I 
