PRESERVATION FOR THE HERBARIUM. 
43 
the fructifications mature. We should rather, as a general 
rule, advise their being gathered just as the masses of 
spores reach their full growth. If, however, more than a 
single specimen of each kind is preserved, the perfectly 
mature and the incipient states of fructification should 
also be gathered ; but in the majority of cases the inter- 
mediate state will afford the best materials for subsequent 
examination and recognition. Certainly the fructification 
is to be preferred in an early rather than a late stage of 
development. 
Of course, when the species produces two or more kinds 
of fronds, examples of each must be preserved, as, for 
instance, in the Allosorus crispus, the fertile fronds of 
which alone would convey but a very indifferent notion 
of the plant. The necessity of attending to this point is 
even more strikingly apparent in such exotic genera as 
the Struthiopteris, and almost all the species belonging to 
the Acrostichum group. 
After being thoroughly dried under pressure, the speci- 
mens, according to their size, should be arranged, singly if 
large, or in groups resembling the natural tufts if suffi- 
ciently small, on one side only of a series of sheets 
(technically half-sheets, Le, single leaves) of stout white 
