7O THE ORCHID REVIEW. 
curiously tessellated with two shades of green—a peculiarity for which, as in 
the case of the variegated leaves of Ancectochilus, I believe no satisfactory 
explanation has been given. 
Yet another modification is the development of an epiphytic habit, as in so 
many of the commonly cultivated Orchids, and this is clearly another 
provision for allowing the tropical forest species to reach the light and air. 
Correllated with the epiphytic habit—at all events in a large number of 
cases—is the development of variously thickened stems or fleshy pseudobulbs, 
an evident provision for enabling the plant to pass safely through the dry 
season. Then we get erial roots with their modified structure and special 
covering of velamen, all of which peculiarities have their special meaning to 
the cultivator. 
Some of these epiphytes have retained the ancestral character of having 
plicate leaves, as in the Cyrtopodium group, the Catasetum group, &c., 
while others have become conduplicate and coriaceous, as in the Maxillariez, 
Oncidiee, Epidendree, Dendrobiez, &c., and some of the latter do not 
develop thickened pseudobulbs, as Pleurothallis, Masdevallia, &c. 
With the exception of Vanilla the preceding groups are what is termed 
sympodial, that is to say the axis or stem soon ceases to grow, usually at the 
end of the season, and the new growth starts from the side. Opposed to 
this is the monopodial type in which the axis continues to grow in one 
direction from season to season, and bears roots right up the stems. This 
type includes all the Sarcanthez, as Vanda, Aérides, Phalzenopsis, Angreecum, 
&c., a distinct type of growth which every cultivator will recognise as requir- 
ing a different kind of treatment. 
These are the principal types of vegetative structure, though some plants 
are more or less intermediate between two given types, and all these different 
types have their meaning for the cultivator. There are also some special 
forms, which are developments of one or another of the preceding. 
Thus the stem may become much elongated and climbing, as in Renan- 
thera coccinea, which on this account can only be grown successfully in 
situations where the necessary space can be given. The pseudobulbs may 
also become hollow, as in Epidendrum bicornutum and the Schomburgkias, 
which in a wild state are tenanted by colonies of ants, whose presence, 
however, is not necessary to the plant’s existence, as they can be successfully 
cultivated at home. These plants, like the species of Coryanthes, seem to 
provide accommodation for the ants, in return for services rendered by the 
latter in keeping their natural enemies, the cockroaches and other insects, at 
bay. In the case of Coryanthes, the ants do not live within the plant, but 
only among its roots, and although these plants seldom liye long in cultiva- 
tion, I think it is not so much due to the absence of their natural 
protectors, as to the difficulty of providing suitable treatment. They 
