136 PRINCIPLES OF BOTANY, ETC, 
should depend on the trivial circumstance above- 
mentioned. We might here bring forward several 
other examples, but they will easily be found upon 
attentive investigation. : 
§ 181. 
The Cryptogamiz, (§ 139), or the plants of the 
94th class, whose flowers are not obvious to the un- 
assisted eye, must be determined by their fruit. No 
character of these plants should be taken that re- 
quires a magnifier, and the character taken should 
be easily found. The flower of the cryptogamious 
plants is of such a kind that it can be seen only at a 
certain time, often for a very short period, and with 
a high magnifier: in some it has not yet been dis- 
covered at all. It would, therefore, be a very great 
error to select for a generic character a part not 
easily visible, and found with great difficulty. But 
the fruit is very easily seen, and may be examined 
with a moderate magnifier; so that it alone must 
give the character. We have not yet, however, suf- 
ficiently investigated the fruit in all the species of 
Cryptogamiz: there are consequently several gaps 
in this class which remain to be filled up. 
In the Filices, Linnezeus has assumed the mode of 
inflorescence as the generic mark. In some of these 
the fruit stands in rows, in others in circles; some- 
times in the centre, sometimes in the margin or in 
the angles of the leaves. In other plants this cir- 
cumstance is of no use, but in the Filices we are - 
obliged to resort to it. 
The 
