LASTREA. 
107 
under the name of Lophodium, a perfectly unnecessary 
and characterless group. 
Lastrea cristata, PresL 
Crested PricMy-toothed BucTder Fern. (Plate VI. fig. 2.) 
This is the simplest of the British forms of a group of 
species intimately related to each other, and formerly 
known as the Crested Shield Ferns. This group consists 
of the plants to which the several names of L. cristata^ 
uliginosa, spinulosa, dilatata, and wmula, have been 
given ; and they form a series so closely connected, that 
some very eminent botanists consider them as all belong- 
ing to two species only, cristata and dilatata, the other 
forms being regarded as mere varieties. This view of the 
subject is, we believe, almost exclusively confined to those 
whose lot it has been to study the Ferns in a general way, 
and mainly from a large suite of herbarium specimens. 
The magnitude of the subject, in such a form, necessarily 
leads to generalizations, and the acknowledgment only of 
the most obvious differences. Those, on the other hand, 
who study a smaller series, confined to certain geographical 
limits — our own country, for example — being unperplexed 
by the magnitude of their subject, are content to admit 
