318 



BEGONIACE^. 



[Diclinous Exogens. 



Order CVII. BEGONIACE^E.— Begoniads. 



Begoniaceae, R. Brotvn in Congo, 464. (1818) ; Endl. Gen. cciii. ; Meisner, p. 336. 

 Diagnosis.— Oiicwr&zYaZ Exogens with dry fruit and placentae projecting and meeting in 



the axis. 

 Herbaceous plants or succulent under-shinibs, with an acid juice. Leaves alternate, 

 toothed, rarely entu-e, oblique at the base. Stipules large, scarious. Flowers pink, in 



c}Tnes. Flowers S ? • Calyx ad- 

 herent. Sepals coloured ; in the 

 (J 4, 2 within the others and smaller ; 

 in the $ 5, imbricated, two smaller 

 than the rest, or 8, of which 4 are 

 petaloid. <J Stamens indefinite, 

 distinct, or combined into a soHd 

 column ; anthers collected in a 

 head, 2-celled, continuous %vith the 

 filaments, clavate, the connective 

 very thick, the cells minute, bm-sting 

 longitudinally. $ Ovary adherent, 

 winged, 3-celled, ■with 3 large 

 placentse meeting in the axis ; 

 ovules anatropal ; stigmas 3, 2- 

 lobed, sessile, somewhat spiral. Fruit 

 membranous, capsular, winged, 3- 

 celled, with an indefinite number of 

 minute seeds ; bursting by sUts at the base on each side of the 

 wings. Seeds wath a transparent tliin testa marked by reticulations, 

 which are oblong at the sides and contracted at either extremity ; 

 embryo very cellular, without albumen, with a blvmt round radicle 

 next the hilum. 



It is not a Uttle curious that the opmions of Botanists concerning 

 the affinity of these well-known plants should remain so midecided up to the present day. 

 I formerly supposed the Order related to Hydrangea from some resemblances in its seeds, 

 &c. ; others have approximated it to Buckwheats on account of the stipules, 3-comered 

 fniit, and coloured calyx. Lmk places it near Umbellifers ; Von Martins next Scsevo- 

 lacese ; Meisner with Spurgeworts ; and the tendency to the production of 4 in the 

 sepals and petals, as evinced by Eupetalum, has led to the opmion that it may be related 

 to the epigynous MjTtal Alliance, its seeds being indefinite and destitute of albumen. 

 And that some near relation does exist between such plants and Begonia, is rendered 

 more probable by Bertolonia maculata, which has the winged fruit and much the habit 

 of that genus. Nevertheless, these are but distant points of approach ; and the real 

 affinities seem to be with Cucurbits, with which Begoniads accord in the unisexual 

 flowers, peculiar stigmas, and even ternary number of the carpels. The discovery 

 by Mr. Hartweg of Begoniads scrambhng up trees and shrubs to the height of 25 feet, 

 renders the resemblance almost complete. To Datisca the relationship seems to be well 

 made out. 



The main objection to the association of Begoniads and Cucurbits in the same Alhance 

 arises from the great apparent difference in their placentation ; that of Begoniads being 

 axile, and of Cucm-bits parietal. But a careful examination of the ovary of DiplocU- 

 nium Evansianum, acuminatum, incarnatum, &c., shows that distinction to be one of words 

 rather than of essential structure. The ovary of such Begoniads consists of 3 carpels, 

 whose dorsal suture is winged, and whose margins turn inwards for a considerable 

 distance, each margin forming a plate or placenta, over which the ovules are arranged. 

 This, with the exception of the wing proceeding from the dorsal suture, is the stinicture 

 of Cucumis, as figured at p. 313, fig. 1, with this diff'erence, however, that the inflexed 

 edges of the carpellary leaves adhere in Diploclinium at a very much more early period than 

 in Cucumis. In Diploclinium acuminatum, when the flower-buds hardly project beyond 

 their fringed bracts, these inflexed edges are easily separable from each other and from 



Fig. CCXX.— Diploclinium Evansianum. 1. a c? flower ; 2. an anther ; 3. a ? flower ; 4. a stigma ; 5. a 

 cross section of the ovary ; 6. a seed ; 7. an emhr3'o. 



CCXX. 



