1 99 
certain Varietal and Hybrid Ferns. 
have reached the equator some are already to be found at the poles, whilst 
still others are scattered over the spindle fibres. The impression is conveyed 
that the irregular chromosomes, which in this fern are not numerous 
although almost always present, fail in some way to respond to the control¬ 
ling influence by which the majority are governed. Such a condition 
indicates a difference in physical and perhaps chemical nature which may 
well be correlated with the variability, and probably also with the sterility, 
of the plants now under consideration. 
When the chromosomes arrive at the poles they still exhibit that same 
‘ indiscriminate ’ and confused arrangement which characterized their pre¬ 
vious behaviour. They also vary much in size and, so far as we have been 
able to arrive at a conclusion, they seem to be inconstant in number also. 
It may be that individuals here and there fail to form bivalents, but when 
the numbers are so great it is difficult to be sure as to this, and we only feel 
justified in recording our impression that such is the case. 
The degeneration of the cells is associated with a degeneration of the 
cytoplasm which becomes more and more marked as the spore mother-cells 
pass through the meiotic phase. This degeneration has been described by 
Tischler 1 and others for a number of hybrids in flowering plants, and it is 
of special interest to encounter it, along with some other characteristics 
of hybrids, in a form which, though a ‘ sport ’, is clearly not of hybrid origin. 
A second feature not seldom to be met with during the nuclear 
divisions of the spore mother-cells of this plant (and, as will appear later, it 
also occurs in the hybrid as well) consists in a curious form of division 
nearly resembling amitosis. We have already mentioned that we found 
a single case in P. vulgare , type. It is to be seen in the spore mother-cells 
produced on both the laciniate and the ‘ reverted ’ pinnae, and it may occur 
in both of the two meiotic divisions. The stage in question usually sets in 
about the time when diakinesis should pass over to the metaphase, though 
it may occur at a still earlier period ; the nuclear membrane remains intact, 
and the ordinary spindle is absent or disappears, the nucleus becomes pulled 
out into a form roughly resembling that of an hour-glass, while the chromo- 
somic contents are numerous, irregular, and small in size. Then the 
nucleus assumes the condition of a double sac, the swollen portions being 
connected together by a tube which becomes narrower as the process 
advances. Fibres then become differentiated in the cytoplasm between the 
two sacs, and even a cell-plate is formed across this interzonal spindle. 
When, as is often the case, the sac-like protuberances are not situated 
symmetrically within the cell, the cell-plate shows corresponding irregulari¬ 
ties. Thus it may be well formed on one side of the connecting tube 
(Fig. 21), but almost absent from the other. Sooner or later the tubular 
1 Tischler, loc. cit. See also Juel, H. O., Beitr. zur Kenntnis d. Tetradenteilung. Pringsh. 
Jahrb. f. wiss. Bot., Bd. 35. 
