210 Farmer and Digby.—On the Cy to logical Features exhibited by 
bipolar from its early appearance, in P. vulgare and its var. elegantissimum 
it is quadripolar in the great majority of cases, in the hybrid it is either 
bipolar or quadripolar, more commonly the latter. 
5. The spindle is formed from a differentiation of the cytoplasm 
(kinoplasm), and it is influenced in its distribution within the cell by the 
aggregation of the chromatic linin within the nucleus. This is especially 
seen in the cases of quadripolar spindle formation. Electrical conditions 
are believed to be concerned in the spindle formation. 
6. Chromatic droplets are ejected from the nucleus into the cytoplasm 
during the early stages of the heterotype mitosis, and also during telophase 
at other mitoses. It is left an open question as to whether this phenomenon 
always implies the same processes. 
7. Nuclear divisions resembling amitosis occur frequently in the 
hybrid, but they also occur, though far more rarely, in P. vulgare (type) 
and in its variety elegantissimum. These divisions are examples of 
imperfect mitoses, and are brought about by the failure of the nuclear 
wall to disappear at the end of diakinesis. 
8. Much irregularity as to pairing of the chromosomes to form the 
bivalents exists in the hybrid plant, and also, though less obviously so, in 
P. vidgare var. e leg an tissim u m . 
9. The processes that lead to depauperation of the reproductive cells, 
and ultimately to sterility, in hybrids are encountered in certain ‘sports, 
which also exhibit sterility in a marked degree \ 
EXPLANATION OF PLATES XVI-XVIIL 
Illustrating Professor Farmer and Miss Digby’s paper on the Cytological features exhibited by 
certain varietal and hybrid Ferns. 
All the figures, with the exception of Figs. 22, 23, and 24, were drawn with the camera lucida 
under a 2 mm. apochr. horn. imm. Zeiss, N.A. 1*40 with comp. oc. 18. x 2250. 
Fig. 22 was drawn with the camera lucida under a 3 mm. apochr. horn. imm. Zeiss, N.A. 
1*40 with comp. oc. 6. x 498. 
Figs. 1-5. Polypodium aztreum. 
Figs. 6-13. Polypodium vulgare. 
Figs. 14-18. Polypodium vulgare var. elegantissimum . 
Figs. 19-21. Polypodium vulgare var. elegantissimum (‘ reverted ’)• 
Figs. 22-34. Polypodium Schneideri. 
PLATE XVI. 
Fig. 1. Polypodium aureutn. Early heterotype prophase in the spore mother-cell nucleus. 
‘ Chromatic droplets ’ are being given off from the nucleus; some lie free in the cytoplasm, whilst 
others are still attached to the nuclear contents by fine connexions, x 2250. 
