174: PRINCIPLES OF BOTANY, &TC. 
rolla: The calyx and corolla indeed remain con: 
Stant in their number in both genera; but this ex- 
ample ought not to be imitated. 
§ 161. : 
The monophyllous and palyphyHous calyx may consti 
tute genera; but not the number of the lacinia or 
leaves. The same thing may be said of the corolla. 
There are some families in which the calyx is of 
importance; but in these the number of the la: 
ciniz or foliola is not taken into account. If twe 
plants resemble one another, but the one has a mo- 
nophyllous and the other a polyphyllous calyx, they 
must be considered as different genera. The reason 
of which is, that a monophyllous calyx never 
changes into a polypetalous one; but the number 
of the foliola of a polypetalous calyx, or the num- 
ber of laciniz ma monophyllous one may be sub: 
ject to variation. ‘The same rule applies to the co- 
rolla. 
§ 162. 
The number of the stamina must be ascertained by 
the greatest number of flowers; but if the flower first 
evolved differs in number of stamina from the rest, we 
must reckon by it. 
‘The flowers of some plants are not always con- 
stant in the number of stamina; in this case we 
must be guided by the greater number ; after, how- 
ever, examining a considerable quantity of flowers. 
Sometimes indeed there appears a variety in the 
number of stamina, the first evolved flower having 
more 

