456 Gregory. — Spore- Formation in Leptosporangiate Ferns. 
hybrid will be perfectly regular, and in our present condition of inability to 
recognize qualitative differences between chromosomes alike in form, we 
should further expect that the mitoses will differ in no visible way from 
those of the pure paternal and maternal races. Cannon has shown this 
to be the case in race-hybrids of Pisztm sativum , a result which is confirmed 
by my own observations upon race-hybrids of Lathyrus odoratus , for the 
material of which I am indebted to Mr. Bateson. 
The sterility which characterizes many hybrids follows upon the 
abortive development of the sex-cells, and the suggestion has been made 
that this may be due to the inability of the hybrid to separate, in the 
formation of the gametes, the characters which were united in the hybrid 
zygote. It is well known that sterile plant-hybrids are particularly 
characterized by abortive development of the pollen, or (in the case of the 
hybrid Fern described by Farmer) of the spores. 
Among the offspring of a race-hybrid of Lathyrus odoratiis fertilized 
with its own pollen, Mr. Bateson obtained a number of individuals which 
failed to form good pollen. In the plants with coloured flowers the 
sterility was, with a few exceptions, correlated with the development of 
a somatic character — the sterile plants generally possessing a green leaf 
axil, while the fertile coloured plants with rare exceptions had red axils. In 
these plants the divisions of the vegetative cells are quite normal, as are also 
those of the archesporium up to the formation of the pollen-mother-cells. 
The irregularity makes its appearance only in the heterotype division. 
The longitudinal fission of the spireme takes place quite normally, but 
the segmentation into chromosomes is, if carried out at all, irregular, and 
the pollen- mother-cells degenerate. Since the equation divisions are quite 
normal, this would seem to indicate that the union of the chromosomes in 
synapsis is such as to prevent any subsequent separation, the result being 
that no sex-cells can be organized, since the essential condition of 
a qualitative separation of the chromatin is not fulfilled. 
Postscript. 
Since the above was written Strasburger’s paper ‘ Ueber Reduktions- 
teilung ’ (Sitzungsberichte d. k. preussischen Akad. der Wissenschaften, 
Mar. 24, 1904) has been received. Strasburger finds that a true reduction- 
division takes place in Lilium spp ., Tradescantia virginica and Galtonia 
candicans , the last-named affording very clear evidence. In the pollen- 
mother-cells of Galtonia six bivalent chromosomes are formed by the 
segmentation of the spireme thread. Each of these undergoes a transverse 
fission into two equal limbs. Not until after this fission does the bending 
of the limbs upon one another take place, so that the bivalent chromosomes 
form 1 1 -shaped, instead of U-shaped, bodies. In this plant then the 
transverse fission takes place at a very early stage. This condition may be 
compared with the variation in the time of fission which has been observed 
in the Ferns (p. 448 and Figs. 15, 16, 23). 
