On the Germination of the Spores of Ferns. 347 
vesicle, in the interior of the embryo-sac. The other end, pro- 
jecting into the canal, dies away. This phenomenon must not 
be confounded with the forcible tearing of the spiral filaments 
just alluded to. Through the union of the germinal vesicle and 
the embryo originates the embryonary globule, which is only 
attached below to the bottom of the cavity contaiming the em- 
bryo-sac by a very delicate filiform suspensor. With the growth 
of the embryonary globule the colourless nuclear papilla dies, 
dries up, and the canal in particular becomes coloured brown. 
In this condition it persists for a long time upon the now ex- 
panding cavity of the nucleus. Usually only one of the nume- 
rous naked ovules produced upon the pro-embryo developes its 
embryo. This need not appear wonderful, since similar examples 
are not wanting in the vegetable world, as in many Palms one 
alone of the three original cavities is regularly perfected. A spe- 
cial reason may be looked for here in the minute size of the pro- 
embryo, which does not afford sufficient nutriment for several 
embryos. With the further development of the one embryo the 
other rudimentary ovules die. In these the foramen of the pa- 
pilla expands, and allows the dead spiral filaments and the rest of 
the contents to escape. The canal, and especially the cavity for 
the embryo-sac, then exhibit a brown colour. The latter may 
be most distinctly recognized in this condition. In vegetating 
ovules, on the contrary, this part can only be observed by a most 
careful extraction of the single organ. For while on the one 
hand it is covered by the still erect nuclear papilla, the detection 
of it is on the other hand rendered impossible by the want of 
any peculiar colour or otherwise distinguishing outlines. Of all 
the species which I have examined, Polypodium aureum is, next to 
Pteris serrulata, the best-adapted. The impregnation follows 
exactly the above-described type in all families, gencra and spe- 
cies ; an exceptional occurrence is the appearance, on the margin 
of the pro-embryo, even in its earliest stage, of a spiral- filament 
organ differmg somewhat in structure, as it loses its uni-cellular 
aspect. Five or six parietal cells are formed which inclose in the 
middle a space either filled with spiral filaments, cellules or hol- 
lows. These structures must be regarded as monstrosities of the 
spiral-filament organs, since they occur abnormally and on in- 
dividuals which never produce an embryo. Such an infertile 
pro-embryo either decays soon after its origin, or, passing into a 
succulent state of growth, appears much larger than is natural. 
In this condition it acquires a resemblance to a Marchantia, and 
usually produces a great number of abortive ovules.” 
This extract has reached such a length that we have not space 
to give an account of the author’s description of the develop- 
