173 



Affinities. Little is at present known of the real characters of this 

 curious order. Only 2 of its genera, Mniopsis and Lacis, have been well 

 described, and even these are still but imperfectly understood. Dr. Von Mar- 

 tius has the following remarks upon it : " It is very doubtful in what part of 

 the natural series Podostemere should be arranged ; for they are connected 

 with so many other orders, in so various and complicated a manner, that it is 

 highly probable that several genera, the affinities of which will be more appa- 

 rent, still remain to be discovered. Nothing can be more singular than the 

 mixture of different characters which they exhibit. Thus, the structure of 

 their spathes, and the want of a true calyx and corolla, approximate them to 

 Naiades (Fluviales) and Aroideaa, while the character of their stamens and 

 fruit is very much that of Juncaginese ; the former of these, however, differ in 

 their lower degree of organization, and the latter in the presence of a more or 

 less perfect perianthium, and in the composition of their capsule. Lemna, a 

 genus closely allied to Aroideaa, seems to be more related to them in its spatha, 

 hypogynous stamens, habit, and mode of life, but is distinguished by its less 

 highly developed few-seeded fruit. Again, Mniopsis, in its ramification, in the 

 form and position of its leaves, and in its stipule, and Lacis and Podostemum 

 in the character of their spatha and the emersion of their pedicels at the time 

 of flowering, call remarkably to mind the habit of Jungermanniae ; so that we 

 should probably not be far from the truth, if we were to say that this order 

 forms a transition from Naiades (Fluviales) to Juncaginea?, on the one hand 

 touching upon Aroidese, thus being, as it were, a sort of noble analogy of 

 Hepaticse among monocotyledons." Nov. G. el Sp. 1. 7. Upon this it is 

 difficult to make any additional remarks, without being in possession of a more 

 complete knowledge of their structure. I must, however, observe, that it 

 appears to me clear that Podostemeae are not monocotyledons, as Von Mar- 

 tius, Kunth, and Richard, suppose, but dicotyledons ; for which I have to offer 

 the following reasons : In the first place their habit is that of dicotyledons, 

 and not of monocotyledons' ; Podostemon being very like a starved Pepper, 

 and Hydrostachys having its flowers in spikes resembling those of Saururus. 

 Tristicha has minute scale-like leaves, imbricated in 3 rows, like which there 

 is nothing among monocotyledons. To this may be added the binary division 

 of the ovarium, which is analogous to that of many dicotyledons, but a very 

 rare structure among monocotyledons. Finally, the vernation of the leaves of 

 Mourera of Aublet (t. 233), and of Marathrum, which is perhaps not distinct, 

 is entirely that of dicotyledons, rather than of monocotyledons. I incline to 

 place the order in the neighbourhood of Piperaceae, to which it probably 

 approaches more nearly than to any plants hitherto discovered. 



Geography. Natives of still waters and damp places in South Ame- 

 rica and the islands off the east coast of Africa ; 1 species is found in North 

 America. 



Properties. Unknown. 



Examples. Lacis, Podostemum, Hydrostachys. 



CLXIV. CALLITRICHINEiE. 



Callithichineje, Link Enum. 1. 7. (1821); Dec. Prodr. 3. 71. (1828); a sect, of Haloragea?. 

 Lindl. Synops. 242. (1829.) 



Diagnosis. Achlamydcous herbaceous dicotyledons, witha4-celledovarium, 

 and solitary peltate seeds. 

 Anomalies. 



