1 93 
certain Varietal and Hybrid Ferns. 
capable of germination. The causes for this will become evident later 
on. Our material was fixed with special precautions, and we found Flem¬ 
ming’s and Hermann’s solutions, in various strengths, to give the best 
results. The stains we chiefly employed were Heidenhain’s haematoxylin, 
Flemming’s triple, and the Polychrome methylene blue and orange tannin. 
The latter gave very sharp differentiation, and may be recommended as 
a valuable addition to the stains in more general use. 
In order to elucidate the peculiarities of the hybrid it is obviously 
necessary to study the meiotic divisions in the parent forms, in order 
to ascertain whether the influence of either parent preponderates in the 
cellular structure of the hybrid. It at once becomes evident that there 
is a great difference between the numbers of the chromosomes in the two 
species. The haploid nuclei of P. anreum contain about 34 (PI. XVI, Fig. 4), 
those of P. vulgare var. elegantissimum at least 90 (PI. XVII, Fig. 19), and 
our impression is that this number may' be too low. P. vulgare (type) 
resembles its elegantissimum variety in respect of these numbers, that is, 
there are about 90 haploid chromosomes (PI. XVI, Fig. 10) or perhaps 
somewhat fewer. The exact numbers are of relatively little moment ; the 
comparative differences form the main point of interest. The hybrid plant 
possesses distinctly more chromosomes than either P. vulgare elegantissimum 
or the type form, but they do not, at least usually, amount to the sum 
of those of the two parents. They are variable, and commonly range from 
95 to 105, but they do not, in the great majority of cases, amount to 124, as 
they should do if they represented the sum of those contributed by the 
parents. These facts are of interest in view of the relative numbers that 
have been given for other hybrids, and we shall discuss their significance 
later on. We will now proceed to the more detailed description of the 
features as exhibited by the plants themselves. 
Polypodium aureum. 
The sporangia of this fern are produced in great abundance. Their 
development follows the ordinary course, a flattened tapetal cell being cut 
off from the tetrahedral archesporium ; the former then divides tangentially 
into two layers, the outer of which retains the tabular shape whilst the inner 
layer becomes glandular in appearance. The sporangium grows faster 
in the peripheral region than in its central sporogenous portion, and by the 
time the spore mother-cells are formed and begin to separate from each 
other they lie as a hollow cluster in the centre of the sporangial cavity. 
The tapetal cells begin to break down as the nuclei pass into the stage 
of synapsis, the glairy mass to which they give rise forms a plasmodial 
nucleated substance bathing the spore mother-cells, and the nuclei of 
these nutritive cells can still be recognized at much later stages. 
O 
