4S2 



PODOSTEMACEiE. 



[Hypogynous Exogens. 



Order CLXXXII. PODOSTEMACEiE.— Podostemads. 



Podostemese, Richard and Kunth in Humh. N. G. et Sp. 1. 246. (1815) ; Martins Nov. G. et Sp. 1. 6. 

 (1822) ; Bartl. Ord. Nat. 72. (1830); Bongard in Mem. de I' Acad. Imp. Peter sb. VI. ser. III. 69. 

 (1834) ; Endl. Gen. Ixxxv. ; Meisn. Gen. p. 122. ; Griffith in Atm. Sc. Nat. ser. II. 9. 183. 



Diagnosis. — Rutal Exogens, with many-seeded fruit, ivhich is finally apocarpous, and 

 apetalous very imperfect flowers. 



Herbaceous branched floatiBg plants without stomates or spiral vessels, and with the 

 habit of Liverworts or Scale-mosses. Leaves capillary, or linear, or lacerated 

 irregularly, or minute and densely imbricated, decurrent on the stem, 

 with which they are not articulated. Flowers axillary or terminal, 

 inconspicuous, usually §, naked, or with a very imperfect calyx, or 

 with 3 sepals bm'sting through an irregularly lacerated spathe. Sta- 

 mens hypogjTious, varying from 1 to an indefinite number, either 

 placed all round the ovary or on one side of it, distinct or monadel- 

 phous ; anthers oblong, 2-celled, bm'sting longitudinally. [Pollen shaped 

 like an hom'-glass, consistuig of two spherules, mseparably united in 

 Podostemon. — Griffith.^ Ovary 2- or 3-celled, with numerous ascending 

 anatropal ovules attached to a fleshy central placenta ; styles or stigmas 

 2 or 3, acute and sessile. Fruit sUghtly pedicellate, ribbed, capsular, 

 opening by 2 or 3 valves, which fall off from the dissepiment, which is 

 parallel with them. Seeds numerous, minute, containing an exalbumi- 

 nous dicotyledonous orthotropal embryo. 



Von Martius has the following remarks upon this curious Order. 

 " It is very doubtful in what part of the natural series Podostemads 

 should be arranged ; for they are connected with so many other Orders, 

 in so various and complicated a manner, that it is probable that several 

 genera, the affinities of which will be more apparent, still remain to be 

 discovered. Nothing can be more singular than the mixture of different 

 characters which they exhibit. Thus, the stinicture of their spathes, 

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

 (Fluviales) and Arads, while the character of their stamens and fruit 

 is very much that of Juncaginacese ; the former of these, however, 

 differ in then' lower degree of organisation, and the latter in the 

 presence of a more or less perfect perianth, and in the composition of 

 their capsule. Lemna, a genus closely allied to Ai-ads, seems to be 

 more related to them in its spathe, hypogjTious stamens, 

 habit, and mode of Ufe, but is distinguished by its less 

 highly developed few-seeded fruit. Again, Mniopsis, in 

 its i-amification, in the form and position of its leaves, 

 and in its stipules, and Lacis and Podostemon in the 

 character of their spathe and the emersion of their 

 pedicels at the time of flowering, call remarkably to 

 mind the habit of Jungermannia ; so that we should 

 probably not be far from the tnith, if we were to say 

 that this Order forms a transition from Naiads (Flu- 

 viales) to Juncaginaceae, on the one hand touching upon 

 Arads, and being, as it were, a sort of noble analogy of 

 Liverworts among Monocotyledons." — Nov. G, et Sp. 1 . 7. 

 So far as the general appearance of Podostermads is con- 

 cerned, this account of them may be received ; but since 

 they have a dicotyledonous not monocotyledon ous embryo, 

 other affinities must be looked for. Bongard first represented their true structure, and 

 more recently Mr. Griffith has described two Indian species of Podostemon, with his 

 habitual accm'acy ; entirely confuining the view which I upon mere theoretical reasoning 

 formerly took of their being Exogens. — Ed.pr. p, 190. And I am still of opinion that 

 if we have among Exogens one type of structure more nearly approachmg that of 



Fig. CCCXXXIII. — The ^ of Hydrostachys verruculosa. 1. the calyx ; 2. the same opened to Bhow 

 the ovary ; 3. a seed ; 4. a vertical section of ii.—Decaisne. 



iWA 



Fig. CCCXXXIII. 



