APOSPORY IN PERNS. 
159 
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 vege- 
tative 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 apo- 
spory, of which the latter gentleman is the discoverer, viz., 
Polysticlium angulare, var. pulcJierrimum. Here flattened 
organs, of undoubted prothalloid nature, are formed by simple 
vegetative outgrowth of the tips of the pinnules, and without 
any connection with sori or sporangia. At first the tip of the 
pinnule merely extends, so as to form a flattened expansion 
one layer of cells in thickness, and with a very irregular 
margin; while the whole tip curves downwards, and often 
forms a spiral coil of one or one and a half turns, closely 
covered above by the more expanded portion of the pinnule. 
In other cases the outgrowth may assume very irregular forms. 
Ultimately the characteristic marginal growth begins at some 
point, sometimes terminal, but more frequently lateral. The 
details of this development have not yet been fully investi- 
gated. The result, however, is the formation of a flattened, 
often heart-shaped, expansion, with a thickened cushion similar 
in structure to that found in normal prothalli ; it bears 
antheridia and archegonia of normal structure ; sometimes, as 
occurs also in ordinary prothalli, they are found both on the 
lower and upper surfaces. A point worthy of note is that in 
those prothalloid structures which are taken directly from 
living leaves in the normal position, without further culti- 
vation, the antheridia and archegonia have not opened; no 
doubt this is due to the want of water, which, as is well 
known, is necessary for this process. I have not yet been 
* Since the above was written the cultures at Kew have progressed, so that 
prothalli bearing archegonia and antheridia may be seen, still connected at 
their bases with the pinnule of the parent plant.— Feb. 11, 1885. 
