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XXVI. On the Origin Ge so-called Scorpioid Cyme. 
By the Rev. GzoncE Hunsiew, M.A., F.L.S., F. G.8., F.O.P.S. 
(Plate LXXXV.) 
Read November 6th, 1879. 
Part I. (Descriptive). 
Ina paper in the Transactions of the Linnean Society (sec. ser. Botany, vol, i. p. 37) I 
have shown that when a stem or branch with opposite and decussate leaves below, bears 
alternate leaves above, the arrangement of the latter is very generally represented by the 
fraction 2, inasmuch as the order of the leaves at once assumes a spiral direction, indi- 
cated by drawing a line from leaf to leaf the nearest way round to each successively, and 
that three pairs of opposite and decussate leaves will thus form one cycle, the sixth 
leaf being (both originally and finally) over the first, in this alternate arrangement. 
There is, however, another method of arrangement, in which, instead of forming a 
continuous spiral line round and round the axis, a line drawn to each successive leaf 
returns after reaching every two successive leaves, so that it forms a curved zigzag line, 
the curvatures oscillating through three quarters of a circle (Pl. LX XXV. fig. 1). 
I first observed this method of change from opposite and decussate leaves to alternate 
in the foliage of a Lagerstremia in the Palm-stove at Kew, and recorded the observation 
in a note at the end of my paper referred to above. 
I have now found that a similar “ oscillating ” arrangement occurs sd the flowers 
and bracts of what are usually called scorpioid cymes, and which, as the sequel will show, 
are not definite in character, but may be more correctly termed scorpioid racemes. 
Fig. 1 represents a projected arrangement of the foliage of Lagerstremia, in which it 
will be seen that the first two pairs of opposite leaves that ** broke up " follow the usual 
spiral order; but from leaf number 4 the spiral returns and henceforth follows the 
* oscillating " method, as I propose to call it. 
Lathrea squamaria is another very illustrative plant. On the lower part of the stem 
the leaf-scales are opposite and decussate, while the bracts (though retaining the same 
relative positions as the scales, and therefore arranged in four vertical rows at angular 
distances of 90° apart) have become alternate by slight developments of the internodes. 
Every bract bears a flower in its axil; so that the inflorescence consists of a dense spike 
of four vertical rows of flowers, all, however, being twisted to one and the same side. | 
In this species I found several combinations of the above two methods of resolving 
opposite into alternate arrangements. The bracts usually commence on a spiral line for 
two or three coils, as in Lagerstremia, but then follow the oscillating method. 
In one case (fig. 2), commencing on a spiral line to the right as far as the 4th bract, 
the line then reversed the spiral direction to the 8th bract; the oscillating method was 
