APPENDIX. 
IOQ 
tative 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 inves- 
tigated. 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. 1 have not yet been 
able to observe the formation of young Fern-plants on these 
prothalli ; but it may be hoped that from cultures now in 
progress at Kew and elsewhere further evidence may be 
obtained on this point. 
This Polystichum is thus an example of the formation of 
an expansion of undoubted prothalloid nature, bearing sexual 
organs by a process of purely vegetative outgrowth from the 
Fern-plant — that is, there is a transition in this case from the 
sporophore generation to the oophore by a vegetative growth, 
and without any connection either with spores or, indeed, with 
sporangi or sori. It may be regarded as a still more complete 
example of apospory than that of Athyrium Filix-foemina, var. 
Clai issima. 
