550 Mr. MiERS on some new Brazilian Plants 



the space between the true pericarpium and the cohering perlanthium consists 

 of a mass of long, transverse cells ; excepting that upon the three placentae, 

 as well as on two longitudinal lines in the middle of each intervening space, 

 the membranes approach each other with scarcely any cellular tissue between 

 them, and upon these lines the fruit easily separates (from its being necessarily 

 weaker at those points as the capsule dries and ripens) into three broad and 

 three narrow valves, without exhibiting any trace of those longitudinal nerves 

 which usually form a distinct margin to capsular valves. In Dictyostega and 

 the related genera there exists but a small quantity of cellular tissue between 

 the true ovarium and adnate perianthium, and hence the capsule is almost 

 membranaceous when ripe ; but in a similar position to that exhibited in 

 Orchidece, is to be seen only a single line where the two membranes closely 

 approximate, and which in like manner sometimes become ruptured from a 

 similar cause, when the capsule ripens, and hence the separation into three 

 imperfect valves is effected not by any regular fissure, but by an irregular 

 laceration of the adhering membranes at those points where they are not 

 strengthened by intervening tissue. On comparing also the seeds of Pleu- 

 rothallis pectinata with those of Dictyostega orobanchioides, there appears 

 scarcely any difference between them either in shape or structure, both pos- 

 sessing a diaphanous reticulated testa many times larger than the nucleus : 

 in Pleurothallis, however, the reticulations are much smaller and more 

 regular, and the cells constituting the areolse are marked with spiral fibres 

 bearing some resemblance to the spiral cells occurring in the leaves of that 

 genus : on the other hand, the areolse of the seeds of Dictyostega are much 

 larger, longer, more transparent, and destitute of fibres. In regard to the 

 included nucleus, the two genera offer a striking analogy, as it is in both 

 inverted, and suspended by an elongated base from the attenuated apex of 

 the rostelliform seed, and in both presents its nipple-like apex towards the 

 hilum. 



Besides the points of resemblance already mentioned, these plants present 

 in other respects a striking approximation to Orchidece, especially to the 

 section of Pleurothallecc, which often possess a simple erect stem with im- 

 perfectly developed leaves, and are not unfrequently destitute of the pseudo- 

 bulbs, so characteristic of the tribe: they often exhibit also a regular six- 



