186. THE REV. G. HENSLOW ОХ THE ORIGIN OF FLORAL ZESTIVATIONS. 
tration of opposite foliage-leaves coalescing in venation in a valvate manner is seen in 
some species of shrubby Veronice. 
Of course there are instances of a valvate calyx accompanied by an alternate arrange- 
ment in the foliage-leaves, such as Malva. These, as also all ** open” kinds of xestiva- 
tion, may be and probably are due to degradation, in consequence of which the parts only 
¢row just sufficiently large to meet in the former case but not overlap, or else, as in the 
latter instances, to fall short of one another altogether, as in the Umbellifere. 
V. REVERSAL OF THE SPIRAL. 
А peculiar feature to be noticed is the frequent reversal of the direction in which the 
parts of successive whorls run, whether of the corolla in being different from the calyx, 
or the inner whorl of a monochlamydeous perianth from the outer. Of the 35 diagrams 
in Le Maout and Decaisne which have both calyx and corolla quincuncial, two have the 
calyx right-handed and the corolla left-handed. Оп the other hand, four have the calyx 
left-handed, while the petals form a right-handed spiral. All the rest have the calyx and 
corolla either right-handed or left-handed together *. 
In examining several flowers of the same species, as in other matters, so in reversal, 
I found many single kinds of plants furnishing this phenomenon, as Crocus and Malva 
sylvestris, in which the right-handed and left-handed contortions were in equal pro- 
portions numerically. 
VI. THE NUMERICAL ORDER OF THE PARTS OF WHORLS. 
In examining the 34 instances of dicotyledonous Angiosperms, where both calyx and 
corolla are arranged on the quincuncial plan, the first petal of the corolla was found to 
be in 13 instances between the 1st and 3rd sepals; in 11 instances between the 1st and 
4th sepals; and in 1 instance between the 5th and 8rd sepals. In all these cases the 
imaginary spiral line would be in the same direction, though not continuous from the 
5th sepal to the Ist petal. 
In 9 instances the spiral has to be retraced to discover the 1st petal. Of these latter 
in 3 instances the 1st petal lies between the 5th and the 2nd sepal, and in 6 instances 
* With regard to the direction of the spiral, I always signify as right-handed the parts of a whorl the sections of 
which, as represented by a diagram, overlap on the right side, as seen from the centre, 1. е. corresponding with the 
movement of the hands of a watch. I find this method more convenient for diagrams than the reverse, which is 
employed іп the terms sinistrorse and dextrorse for spiral climbers. In that case it is more convenient to regard the 
spectator as being on the outside ofthe climber. Prof. A. Gray (l. c.) says :—‘ I note with satisfaction that Bentham 
and Hooker use these terms to signify from left to right or from right to left of a person supposed to stand outside 
of a closed bud, which is surely the natural position of the observer.” This is without doubt perfectly true for 4 
bud, but it is not for a diagram, which is a transverse section of a bud. In this case it is “ natural ” for the eye to 
rest on the centre. People invariably regard the hands of a watch as going from left to right; yet if instead of 
Tegarding yourself in the middle of the watch, you remember that уоп are outside of it, then the hands go from 
right to left when passing from 3 to 9 o'clock. 
There appears to be some confusion in Le Maout and Decaisne’s work; for they describe their diagrams, р. 80, of 
phyllotaxis as left-handed, though they are really right-handed if traced from the periphery to the centre; yet the 
descriptions of the two convolute corollas of Hermannia, р. 284, correspond to the method I һауе adopted; compare 
also the diagram of Dianthus, p. 256 which, again, is co i ibed i 
у again, ntrary to the latter, and is left-h though described in 
the text as ri and is anded, ug. 
