io8 
APPENDIX. 
If pinnules showing the above characters be subjected to 
favourable conditions of heat and moisture, the vegetative 
development of the sporangia may proceed at once. On pinnules 
laid on damp soil, and forced quickly in the propagating-pits at 
Kew, the earlier stages of this further development have been 
traced. The details show great irregularity; and they are found 
to correspond to the greater or less completeness of arrest in the 
normal development of the sporangium. Thus, sporangia which 
show a clearly marked annulus do not usually assume any further 
vegetative activity ; those, however, which are arrested at an 
earlier stage in their normal development may produce, by a 
purely vegetative process, outgrowths of very irregular form. 
Sometimes all the superficial cells of the club-shaped body may 
take part in the process, and this is most clearly seen where the 
arrest of the normal development is most complete. In other 
cases the head of the arrested sporangium may be thrown off, 
while the stalk continues its vegetative growth. The result is in 
either case the formation of flattened structures, consisting only 
of parenchymatous, chlorophyll-containing cells, which, sooner 
or later, show at one or more points on their margins that 
growth with a wedge-shaped, apical cell, which is well known 
as characteristic of the Fern prothallus ; root-hairs are at 
the same time formed by the outgrowth of individual cells. 
None of my cultures have as yet formed sexual organs : this 
we must wait for ; but meanwhile it may be remarked that 
Mr. Druery’s observations during the last two years show 
that, in the cases observed by him, sexual organs were 
formed, and young Fern-plants were produced by them. In 
any case, however, the above observations show that in the 
Fern in question there is a transition from the sporophore 
generation to a structure of a prothalloid nature, without the 
intervention of spores, and that it is formed, by a process of 
purely vegetative growth, from more or less reduced sporangia. 
Finally, it may be stated that my observations do not exclude 
the possibility of a formation of such structures by a vegetative 
outgrowth of the base of the sorus itself ; whether this actually 
occurs must be decided by further investigation.* 
Through Mr. Druery I have Mr. G. B. Wollaston’s per- 
mission to mention a still more interesting example of apospory, 
of which the latter gentleman is the discoverer, viz., Poly- 
stichum angulare, var. pulcherrimum. Here flattened organs, 
of undoubted prothalloid nature, are formed by simple vege- 
* Since the above was written Ihe cultures at Kew have progressed, so 
that prothalli bearing arclugouia and anlheridia may he seen, still 
connected at their bases with the pinnule of the parent plant. — 
February n, 1885. 
