THE REV. С. HENSLOW ON THE ORIGIN OF FLORAL JESTIVATIONS. 183 
Le Maout and Decaisne endeavour to explain the structure differently, by conceiving 
No. 1 to be one of the wings, No. 2 the other wing, No. 3 a keel-petal, No. 4 the 
standard, and the remaining keel-petal No. 5. "They thus derive it from the quincunx 
by removing the standard from being entirely within to a position entirely without 
the rest (fig. 466, p. 87). Similarly with regard to the :estivation of the Cesalpinee as 
represented by the diagrams of Cassia and Cercis (р. 367), though in these some con- 
fusion in the explanation is made by those authors; for in describing (on p. 87) these 
diagrams, they вау,--“ The standard retains its normal position [ż. e. within the others], 
and the quineunx is properly formed." But in reference to the diagrams given in 
p. 367, this is clearly not the case. Both in that of Cercis and that of Cassia, if we 
take the outermost of the two anterior petals as No. 1, then No. 2 (whether the spiral be 
supposed to turn to the right, as in Cassia, or to the left, as in Cercis) is in neither case 
external also, as it ought to be for a quincuncial or pentastichous arrangement. If, 
however, we take, as I propose, the exterior anterior petal as No. 1, then the internal 
petal as No. 5, both the above kinds fall under this type, which I call half-imbricate. 
It will be seen that No. 1 is not the same petal in both the papilionaceous corolla and 
that of these two genera of Cesalpinee. That this difference is of no relative importance 
will be shown hereafter. It may be remarked here, however, with regard to the standard 
not being identical with the fifth (internal) petal of Cassia, that the wings of the former 
lie over the keel, while in the latter genus it is just the reverse. This would seem to 
show that the papilionaceous resemblance is apparent only and not real. 
The calyx in Cassia is represented as quincuncial, that of Cercis “ open” and therefore 
indeterminate. 
I recommend this interpretation as doing far less violence to the fundamental quincunx 
than that hitherto suggested; in other words, it is acquired by a simple alteration of 
position of one edge only of one petal. It may be observed, too, that it is obtained by 
regarding the parts of the spiral as running in the reverse direction to that according to 
the former method of regarding it. 
This type of sestivation will also account for the so-called “ cochlear,” as of the Snap- 
dragon (Tab. ХХУ. fig. 10, and Те М. & D. fig. 468, р. 87, in which the numbers 
there given should be exchanged respectively as follows, viz. 1, 5, 4, 3, 2 should be 
Written instead of 1, 2, 3,4, 5). Thus by retaining the innermost (anterior) petal as 
No. 5, and by merely shifting No. 2 partially under No. 4, we obtain the sstivation as 
illustrated by the diagram. 
Another illustration of the half-imbricate in connexion with the quincuncial will be 
found in the diagrams of Scerophularineg. The calyx of Scrophularia (р. 585) is strictly 
quincuncial: the exterior sepal, No.1, is posterior *; but if this be compared first with 
the diagram of -Linaria (p. 584), it will be seen that the 2nd sepal (the right anterior) 
now passes under the 4th (or the right), the spiral being right-handed ; and the wstiva- 
tion of the calyx is therefore half-imbricate. It is similar to the calyx of Paulownia 
(р. 584); only this spiral is left-handed. But now comparing these with the calyx in the 
* The diigram is wrongly placed. The left-hand exterior sepal is the posterior one in reality. 
+ On the distinction between right- and left-handed spirals, see below, note, p. 186. 
