536 Farmer . — On the S true hire of a Hybrid Fern . 
strands is, on the average, rather less and their size is 
smaller, than in P. aureum. 
It is not a valid objection to the legitimacy of instituting 
these comparisons to urge that the degree of vascular com- 
plexity and development is merely conditioned by the size 
and luxuriance of the organ concerned. Of course these 
factors proximately determine whether large or small channels 
shall be sufficient, but they do not necessarily affect the 
particular method of arrangement, or the relative proportions 
existing between the various constituent strands. 
Turning to the sclerenchyma which occurs at the periphery 
of the leaf-stalk, it is seen that in this particular also the 
hybrid more closely resembles one parent (P. aureum ) than 
the other. The band is, however, a little thicker, relatively 
to the diameter of the transverse section in P. Schneideri , 
and the cells are somewhat more strongly lignified. In this 
they approach P. elegan tissimum , in which the band is 
proportionately far more highly developed, its cells are 
longer and are dovetailed between each other more effec- 
tively, and are both more thickened and lignified than in 
P. aureum. 
As the leaf-blades of P. Schneideri and P. elegan tissimum 
more nearly resemble each other, a considerable degree of 
similarity might be looked for in their epidermal cells 
and stomata. The resemblance as a matter of fact is fairly 
close (PI. XXIII, Figs. 10, 11), but there are obvious differ- 
ences of detail. Thus the epidermal cells of the hybrid are 
a little larger, although not nearly as large as those of 
P. aureum (Fig. 9), but the guard-cells of the stomata closely 
resemble the guard-cells of the last-mentioned plant, save in 
their smaller size. 
The roots of the three Ferns show a complete series of 
gradations, those of the hybrid standing, on the average, 
exactly halfway between the thin ones of P. elegantissimum 
and the much thicker ones of P. aureum. But the degree 
of variation in the detailed structure of the individual roots 
of even one specimen renders these organs less suitable than 
