THE REV. С. HENSLOW ON THE ORIGIN OF FLORAL ASSTIVATIONS. 195 
arrangement in the bracts or bract-like sepals of the flower, but no differentiation occurs 
between the bracts, sepals, and petals respectively; whereas Chimonanthus (see fig. 
p. 191, in Le M. & D.) would seem to be a more highly differentiated type, in that not 
only is the calyx now distinguishable from the corolla, but five anterior stamens con- 
stitute a distinct whorl by themselves, and the indefinite barren ones of Calycanthus 
are here represented by five also. 
How whorls or cycles of fives arise directly out of opposite parts has been fully described 
in my previous paper, quoted above, р. 181; so that I need not dwell upon it now. 
Magnoliacee, Berberidacee, Апопасее, and Menispermacee are orders characterized 
by a ternary arrangement in their flowers, and by the whorls being usually double. 
The origin of this might at first sight be thought to be the same as of the ternary 
arrangement, which is almost universal in petaloid Monocotyledons—namely, to have 
arisen from the tristichous phyllotaxis. But the fact that the perianth consists 
of 6 parts (=3+3) in the latter, and twice or more than double that number in 
some of the former, is significant, and would seem to imply a different origin, which I 
believe to be as follows :—For any phyllotactical arrangement corresponding to the frac- 
tions of the usual series, excepting 1 or distichous, every projected circle contains three 
leaves; and on arresting the internodes of the flowers there always follows the tendency 
to alternation in position with the parts of the whorls immediately above and below. 
Hence the “threes” of each circle arrange themselves in a decussating manner. Thus 
іп Berberis vulgaris we have З bracts, 6 (—3--3) sepals, 6 (=3-3) petals, 6 (23--3) | 
stamens, making in all 21 parts, corresponding to a cycle of the series 55. 
On the other hand, a flower of Aconitum, according to Braun, as quoted in Sachs’s 
Text-Book, р. 530, is composed as follows: the sepals are pentastichous, or $; the 
corolla octastichous, or 2; the stamens зг, and the carpels 3. 
Hence it would seem that there can be be at least four methods of disposing the 
floral members when numerous and spirally arranged, viz. :— 
1. Spirally and with no breaks, then mostly з, e.g. Magnolia. 
` 2. Broken up into fives, or 2 arrangement . . ,  Chimonanthus. 
3. Broken up into threes, decussating . . . » Berberis. 
4. Broken up into whorls of 5, 8, 21, and 8 . . „ Aconitum. 
XII. Note D.—Owx THE NATURE ОҒ THE COROLLA OF Primula. 
With regard to the theory of Pfeffer (see Sachs's Text-Book, p. 531), that in the 
Primulacee the corolla is an outgrowth of the andrecium, I think there is more 
than one argument against it. Not only would the whole of the Myrsinee have to be 
interpreted in a similar manner, but all analogy seems opposed to it. | That the stamens 
are opposite the petals is true; but then Samolus, with its staminodia alternating with 
the petals, throws light upon this peculiarity; and if we examine the fibro-vascular 
bundles, it will be seen that ten pass into the tube of the corolla, five larger ones up the 
middle of each lobe, and five smaller ones are intermediate; each of the larger sends 
off a small bundle to the stamen adherent to the petal, respectively. Тһе main portion 
