GENERIC DISTINCTIONS IN PLANTS. 
65 
been made of the greatest consequence in forming genera; this part 
had not even a name before Linnaeus had distinguished it, and which 
is a very decisive and sure mark, and can be relied on. 
The stamina and calyx being less subject to luxuriancy are far 
more certain than the petals. The corolla varies as to its figure in 
many genera, and also to number, being in Ranunculus and Helle- 
borus, pentepetalous in some, and polypetalous in others, in Statica, 
pentepetalous, and monopetalous; in Fumaria, dipetalous and tetra- 
petalous, and the number is also variable in the same species, as in 
C'arica and Jatroplia. 
The structure of the pericarpium was formerly thought to be of 
great consequence in determining the genera, but there are examples 
that demonstrate the contrary. There are a great many genera that 
have been established on distinctions in the pericarpium, which are 
now rejected. 
The characters of luxuriant flowers whether eunuchs (deficient of 
stamens) or mutilate (deficient of calyx and corolla) cannot be al¬ 
lowed any place in determining the genera, for in full flowers no 
number of petals can be assigned, and the stamina are generally 
wanting, the number of which makes a part in the generic character; 
and in mutilal flowers, the corolla would be excluded from the des¬ 
cription contrary to the nature of the other species of the genus. 
But as the calyx in full flowers is scarcely ever altered, it may de¬ 
tect the genus, and the lowest series of petals in polypetalous corolla 
remaining the same, in respect to number, the genus may be often 
known by that character, as in Rosa, Nigella, and Papava. 
SPECIFIC DISTINCTIONS. 
Generic distinctions, I have shown to depend on the form of the 
fructification, and to be confined to that alone; specific distinctions 
take their rise from any circumstance wherein plants of the same ge¬ 
nus are found to disagree, provided such circumstance is constant, 
and not liable to variation by soil, culture, or other accidents. 
Hence Linnaeus asserts the species to be as many as there were dif¬ 
ferent forms of vegetables produced at the creation, and considers all 
casual differences as varieties of the same species. I shall now treat 
of those circumstances by which species are determined with cer¬ 
tainty. 
The root often affords a real specific difference, and is sometimes 
the chief distinction, as in Scilla, where the species are scarcely to 
be distinguished but by the bulbs being tunicate, solid, or squamose ; 
and in Orchis where the species are known by the roots being 
G 
