MR. HEMSLEY ON PLATANTHERA CHLORANTHA, VAR. TRICALCARATA. 5 
which may perhaps be accounted for by the fact that the ordinary structure 
is very unusual owing to the suppression of parts and the singular forms 
assumed by those developed. Theoretically the orchid flower consists of a 
perianth of six parts, in two series ; of six stamens, in two series; and a 
tricarpellary pistil. In the great majority of orchids, including Platanthera, 
the six parts of the perianth are all developed, but they often differ very much 
in shape in the same series, and one of the inner series differs so much from 
the others that it has the distinctive name of lip or labellum. On the other 
hand, only one stamen is usually developed. | 
Returning to Platanthera bifolia in the broad sense, that is including 
P. chlorantha, many deviations from the typical floral structure are on record, 
which collectively support the theory explained. 
The kind of deviation just described has been designated false or irregular 
peloria, because the parts concerned belong to different whorls; that is to say» 
two of the spurred organs belong to the sepal-series and one to the petal-series. 
True peloria of two kinds has been observed in Platanthera, namely lip-peloria 
and petal-peloria, in which the transformed organs, being of the petal-series, 
are either like the lip or the lip takes the shape and colouring of the other 
two petals. In some instances of petal-peloria six fertile stamens are developed, 
thus exhibiting a reversion, may we call it, to the ordinary monocotyledonous 
type. Many instances of imperfect peloria are on record, such as the 
conversion of one of the paired petals into a lip-like organ, or, as in some 
cases, only one half of an organ is affected. As I have no practical knowledge 
of anatomical development I will not attempt an explanation of these 
phenomena, but I must say that it seems to me very diffieult to explain whence 
the sepals in the three-spurred Platanthera derive the material for their extra 
development, unless we may assume the foundation of surplus-spur-material. 
The staminodes being present, it is not from that source that material is 
diverted. 
Miss Wilson has written again to say that she found only one spike of the 
three-spurred Platanthera, and that was on the fringe of a wood called The 
Holts, which Нез along a ridge of hill north of the village of Bishop's Caundle, 
about five miles from Sherborne. 
EXPLANATION OF PLATE 1. 
Figures 1 to 3 are more or less diagrammatic and the pose is not quite natural, as the 
median longitudinal plane of the flowers was oblique to the axis. 
. 1. A flower attached to the axis, natural size. 
>, 2, The same about three times natural size, front view. 
3. Back view of the same. 
. 4. Odd sepal, very much enlarged. 
ig. 5, A petal, very much enlarged. 
6. A pollinium and gland, very much enlarged. 
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