64 
GENERIC DISTINCTIONS IN PLANTS. 
their congeners on this account. When the charasteristic mark of 
any genus is wanting, in any particular species, we should proceed 
with caution, lest we confound gepera that should be distinguished ; 
and when this mark of any genus is observable in some species of 
another genus next of kin to it, a like caution is again necessary, lest 
we should multiply the genera, by parting species that should stand 
together. Thus we find in the Sedum, and Cotyledon, the nectary 
adheres to the base of pistillum; in Epilobium and CEnothera, the 
calyx is tubulose, and in Mespilus, and Crcetagus, the structure of 
the flower is alike. The more constant any part of the fructification 
is found, throughout the several species of any one genus, the more it 
may be relied on with certainty, as a characteristic mark of that genus. 
Thus, the nectarium in Hypecoum is constant, but not the siliqua; 
the Convallaria is constant in its spotted berry, but not in its corolla ; 
the Lobelia, in its corolla, but not in its fruit; and the Cassia in its 
corolla, but not in its siliqua. In some genera, one part of the fruc¬ 
tification is found to be most constant, and in others another, but 
there is no part that is not subject to variation ; thus we find the peri- 
carpium variable in the genera of Impatiens and Primula, and the 
seeds in Ranunculus and Alisma. 
If the flowers agree, while the fruits differ, the genus must not be 
parted. Thus in the extensive genera of Hedysarum, Cassia, Acacia, 
&c., a great number of species have been ranged under the same 
genus, on account of the conformity in their flowers, though there is 
variation in the fruit. That the figures of the flowers are more cer¬ 
tain than that of the fruit, appears from any examples, as from Cam¬ 
panula, &c., but there is a great variation sometimes in the propor¬ 
tion of the parts of that figure. The number of the parts is also lia¬ 
ble to variation, and is sometimes found to vary even upon the same 
plant, particularly in Garden Rue, (Ruta graveolens) Adoxa, Tetra¬ 
gon i a, &c., in the flowers of all which the number of the parts vary 
from five to four. In these doubtful cases, the natural number must 
be collected from the primary flower, but in the variation of the 
number of the parts there is a proportionable affinity worthy of re¬ 
mark. In flowers, the stamina usually vary from ten to eight, and 
from five to four; the calyx and corolla from five to four and the whole 
flower from four to three; and the fruit usually varies from five to 
three, and five to four. The situation of the parts is the most con¬ 
stant, very rarely varying in the same genus. 
The regularity of the petals is not so much to be depended upon, 
for we see in geranium, the European species have regular corol¬ 
las, but the African have irregular ones. The nectarium nature has 
