45 
ring stand with respect to each other. It is by no 
means a matter of indifference how that is represented. 
In the Datura the five parts of one ring always 
stand betiueen those of the next ring, and not opposite 
to them. That is the general rule. When an exception 
to it occurs, as in a Lysimachia, a Primrose, or similar 
plant, the circumstance must be carefully noted. It 
sometimes happens that the number of parts in the 
rings of a flower does not correspond. Thei'e may be, 
for instance, five parts in the outer ring, and five in 
the second ; and not Jive , but twice Jive , or some 
other multiple of five, in the third ring; in general, 
indeed, the numbers are all multiples of each other, 
so that if you have three or four in one part you have 
three or four or some multiple of those numbers 
everywhere else. This is one great cause of the 
extraordinary symmetry of flowers; and, however it 
may be hidden, owing to the manner in which 
flowers sometimes grow, it is always ascertainable. 
91. This symmetry of flowers deserves the most 
careful attention. In some shape or other it is always 
present. Even the 
white Butterfly plant, 
unsymmetrical as it 
seems to be, is no ex¬ 
ception. That singular 
flower consists of two 
rings of parts, each 
made up of three. The 
second ring not only 
grows from within, but 
flower OF rirAL.-Exorsis. the parts are placed 
within each other exactly according to rule. Never¬ 
theless, there is an apparent want of symmetry, for. 
