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APPENDIX. 
comprehend, and which were a bar to anything 
like correct observation. It was therefore obvious, 
if the investigation were to be followed up success- 
fully, that some means must be devised for raising 
an unlimited supply of any desired species. The 
usual method of sowing fern-seed, by scattering 
it over damp, sandy mould, is very uncertain, for 
the mould itself will frequently contain the seeds 
of other species ; and even if the crop of plants 
come true to the sowing, it is difficult properly 
to separate sand and other extraneous matter 
from the young frond previously to placing it 
under the microscope, without danger of injuring 
its delicate structure. My plan, therefore, was 
to procure some soft, porous, potter’s ware ma- 
terial that should readily imbibe and retain 
moisture upon which to sow the seed desired to 
be raised. While searching for such material I 
met with a peculiarly fine and soft sandstone, 
admirably adapted for the purpose. This I pre- 
pared by breaking it into pieces of from one to 
two inches square, and less than one inch thick, 
afterwards rendering the faces parallel and smooth 
by rubbing them on a flat stone. The reason for 
thus adjusting the size and smoothness of the 
pieces was simply to facilitate their being placed 
for observation on the stage of a microscope. 
Before sowing the seeds on these prepared pieces 
