xy 
Mancu-Arrit, 1919-]. THE’ ORCHID) REVIEW. 43 
believed that parasitic organisms are not concerned in their initiation, as 
there are no symptoms of local poisoning. Some unfavourable cultural factor 
is suggested as the probable cause. 
Mr. Brierley remarks that in the casual examination of Orchid Spot, as 
specimens have come to hand, seven distinct types of disease have been 
recognised. Of these it is highly probable that four are the result of the 
action of parasitic organisms, one of local chilling of the leaf tissue, one 
probably of atmospheric poisoning, and one of some other physiological 
derangement of the protoplasm, due probably to unsuitable cultural 
conditions. And he has no doubt that there are others. At present all are 
lumped together as ‘‘ Orchid Spot,” and horticulturists endeavour to control 
a disease of physical causation by a fungicidal spray; or a fungal epidemic 
by regulating to a nicety the temperature of the water supply. A detailed 
and intensive study of the subject is much wanted, because it is necessary 
to ascertain the cause of a disease before one can apply a remedy with any 
hope of success. 
| OA 
xi ODONTOGLOSSUM MACULATUM & O. CORDATUM. PS 
QUESTION as to the habitat of Odontoglossum cordatum is raised in 
connection with the origin of the natural hybrid O. Humeanum (pp. 4-6), 
and a search into the records shows a remarkable amount of confusion with 
the allied O. maculatum. 3 
O. corpatum, Lindl., was described in 1838 (Bot. Reg., xxiv. Misc. 
p. 50), and shortly afterwards figured (Kn. & Westc. Fl. Cab., iii. p. 37, 
t. 100), from a plant which flowered in the collection of George Barker,. 
Esq., of Birmingham. The plant had been received from Mr. Ross, who. 
had been sent to Mexico by Mr. Barker, to collect Orchids. Shortly after- 
wards Lindley expressed a doubt (Sert. Orch., sub t. 25) as to whether it was 
distinct from O. maculatum, Llav. & Lex., a species then known only from 
description, but this doubt was removed when some two years later the true 
O. maculatum also bloomed with Mr. Barker. In 1847 a reputed “O. 
cordatum ” was figured by Paxton (Mag. Bot., xiii. p. 147), from a plant 
which flowered in the collection of S. Rucker, Esq., of Wandsworth, but it 
is not that speci@s. It has since been referred to O. maculatum, but we 
believe it is actually a natural hybrid between the latter and O. Rossii, hence 
a form of O. Humeanum (see p. 42). Three years later, O. cordatum was- 
figured under the erroneous name of O. maculatum (Bot. Mag., t. 4878), 
from a plant which flowered at Kew, and this latter Lemaire described as a 
new species, under the name of O. Hookeri (Ill. Hort., iii. Misc. p. 41). In 
1859 the species was again figured and described as O. Lueddemannii, Regel 
