Juty,. 1916.] THE ORCHID REVIEW. 175 
the cells act consequently like traps of light. The rays of light that reach 
the base of the cell are, however, not allowed to pass into the inner 
tissue (mesophyll) of the sepal, being reflected by the concave layer of 
yellow chromatophores (anthoxanthin) aggregated at the base. The 
reflected light, in returning to the atmosphere, either directly or after total 
reflection at the lateral wall, has to pass again through the red sap, hence 
the light issuing from the apex of each cell consists of pure red and pure 
yellow rays only, and each cell becomes a luminous spot of this combined 
colouring. 
Occasion illy one finds a sport of the plant with yellow flowers. This is 
due to the absence of the red pigment in the cell sap of the epidermal cells, 
while the granules of anthoxcyan are still present. A similar combination 
of two pigments exists in D. ferruginea, hence this species also produces, 
although rarely a yellow form. 
\@ 
HESE interesting little plants receive scant attention from Orchidists, 
probably because they are not epiphytes and do not require the 
protection of an Orchid house. They seem to form a class apart, and when 
shown at our horticultural meetings they do not appear before the Orchid 
Committee, but must be searched for among herbaceous and alpine plants, 
where a good many pretty little things appear from time to time. Several 
interesting species of Orchis and Ophrys, and the pretty little Calypso 
borealis were shown at spring meetings of the R.H.S. by Mr. George 
Reuthe and others, and at the Chelsea Show Cypripedium japonicum, 
which is unique in its fan-like leaves, was shown by Mr. Amos Perry, 
together with the modest C. debile, another Japanese species, and one 
with clear yellow flowers which may be referable to the Chinese C. luteum. 
We also noticed examples of the Siberian C. macranthum (sometimes 
wrongly called C. ventricosum) and its chaste variety album, the familiar C. 
Calceolus, and two or three of the North American species. Several of 
the Orchises are very showy when grown under suitable conditions, and at 
the present time O. foliosa, O. latifolia, and what is often known as O. 
maculata superba, are making a good display on the Rockery at Kew. The 
latter is a very puzzling plant, a supposed hybrid between O. maculata and 
latifolia, but the point has never been cleared up. There are forms of O. 
latifolia in bloom with both spotted and unspotted leaves, also O: maculata 
and a very pretty light form in which the markings are pale pink instead of 
purple, several examples of Serapias Lingua, Gymnadenia conopsea, and 
a nice clump of Cypripedium Regine. A little clump of C. macranthum 
HARDY TERRESTRIAL ORCHIDS. \$| 
