162 THE ORCHID REVIEW. [JUNE, Igto. 
THE EVOLUTION OF THE ORCHIDACE, 
(Continued from page 132). 
Tue two remaining subtribes of Epidendree, Pleurothallez and Leliez, 
are natives of the warmer parts of America, and there are strong reasons for 
believing them to be divisions of the same original branch, owing to the 
various points of resemblance between them. 
The Pleurothalleze are the more primitive in structure, and Bentham 
remarks that the chief character of the subtribe resides in the vegetative 
organs and. inflorescence, the pollinary apparatus being that of Liparidez, 
or the pollen masses usually, but not always, smaller and fewer. The 
Pleurothalleze are generally small epiphytes. The flowering stems arise 
from the nodes of the rhizome or of a creeping caudex, and are simple, not 
thickened into fleshy pseudobulbs. They bear at the base, or at 
intervals below the leaf, one, two or more sheathing scales, and 
apparently terminate in a single leaf, either sessile or petiolate, but not 
forming any sheathing base. At the base or in the angle of this leaf is 
the inflorescence, sometimes a one-flowered peduncle, sometimes a 
raceme or a cluster of one or several-flowered peduncles, issuing 
from a sheaf, which is sometimes very minute, sometimes long and spathe- 
like. This inflorescence is in reality terminal, and the leaf lateral immedi- 
ately under it. The secondary stem is generally well-developed, but in 
Masdevallia, and in a few species of other genera, the stem is so much 
shortened that the peduncles and leaves appear to come from the nodes 
of the rhizome direct. Nearly one thousand species of Pleurothallee are 
now known, and these are divided into some twelve or more genera. 
Pleurothallis contains nearly five hundred species, and is distributed 
from South Mexico to Bolivia. The flowers vary much in size and colour, 
but in the majority they are small and green, with the sepals free or the 
lateral pair united, and the petals and lip smaller, the latter being articulated 
to the short foot of the column. The pollinia are two in number. The 
flowers are either borne in more or less elongated spikes or racemes, in 
heads, or sometimes solitary. A good many species are known in cultiva- 
tion, chiefly in botanical collections, but P. Roezlii is often grown for its 
large deep purple flowers, which are borne in drooping racemes. P. 
macroblepharis, Barberiana, astrophora and some others are very graceful, 
and P. ornata is remarkable for the petals being fringed with hair-like 
appendages, which flutter in the slightest breeze and give the flowers a very 
remarkable appearance. These appendages are hollow, unicellular hairs, 
being filled with hair and attached by a very slender elastic base. P. 
scapha, P. insignis and a few other species are also attractive. 
Stelis is much like Pleurothallis in habit, but the sepals are united into 
ie eee Ce 
