138 
APPENDIX. 
site conditions, any species may be raised, if the 
seed sown be fresh and fully matured. 
This principle of raising ferns is applicable to 
several important purposes besides that of the 
facility it affords for observing and studying the 
laws of their development. In the first place 
many kinds now rare and valuable, or even un- 
known in this country from the difficulty of 
bringing them home, even with the protection of 
your glazed cases, might be introduced with faci- 
lity by sowing the seeds in the country where 
they grow,* on some suitable material, whether 
sandstone, Bath brick, tile, wood, bark, or even 
charcoal — wood or bark suggests itself in the case 
of such as are parasitic in their habits — and 
enclosing them in a small glass case, a case so 
much smaller than would be required for full- 
grown plants, that it might be a cabin companion 
for a long voyage. Secondly, it is frequently 
desirable, even in this country, to raise particular 
species with some greater degree of certainty 
than, from various ill-understood causes, is gene- 
rally found practicable. Again, experiments on 
this principle may be tried in a great variety of 
ways until the true habits of obscure species are 
* On referring to your book 46 On the Growth of Plants in Closely- 
glazed Cases,” p. 29, near the bottom, I find that the same idea is 
expressed in reference to the use of surface-mould as a medium. 
