791 



VISCACE.E. 



[Epigynous Exogen.-. 



Fig. DXXIV. quater. 



VISCACE.E. 



•■ Viscoidete, Rich. Ann. dv.fr. 33. (181S) ; Myzodendrere, S. Br. Linn. Tram. 19, p. 232.(1844); 

 Viscaceie, Mkrs Ann. A'at. Bis., 2nd. ser. 8, p. 179. (1851). 



" Parasitical evergreen shrubby plants dichotomously ramose. Leaves opposite, 

 fleshy, veinless, entire. Flowers minute, dioecious or monoecious, generally imbedded 

 in decussate pairs in fleshy axillary spikelets. Calyx confounded with the corolla, 



in a greenish-coloured perigonium, tube urceolate, 



adnate to the ovary, with 3 to 5 fleshy, triangular, 



free, patent lobes, valvate and depressed in 



aestivation : disk epigynous, flat or cup-shaped, 



adnate to perigonium, with 3 to 5 short, rounded, 



free lobes, which are alternate with the segments 



of the perigonium. Stamens equal in number 



and opposite to segments of tbe perigonium, 



almost sessile, inserted on outside of disk between 



its lobes. Ovary 1-celled, with 3 ovules suspended 



from a free central placenta. Berry drupaceous, 



1-seeded; pericarp membranaceous, enveloped in 



fleshy viscous juice : seed solitary, erect, naked ; 



albumen large, fleshy, heart-shaped, with a small 



embryo half imbedded in emarginate summit of 



albumen, the exserted portion covered with a 



nianimseform embryotega, which is an extension 



of the albumen : radicle large, subterete, superior, 



partly exserted, cotyledons very minute, wholly imbedded in the albumen. 



" The affinity of the Viscacese is decidedly with Santalaceae, with which they agree 

 in their monochlamydeous flowers, with the stamens placed opposite the segments of 

 the border, which have a valvate sestivation : the tube of the perigonium is adnate 

 with the ovarium, as well as with the epigynous fleshy cup-shaped disk, the lobes of 

 which are free and alternate with the stamens and the segments of the perigonium : 

 the ovary is unilocular, with 3 ovules suspended from a free central placenta, one 

 ovule only arriving at maturity, and this ripens into an exutive albuminous seed. In 

 all these points they resemble that family, but they differ in their entirely parasitical 

 habit, their opposite leaves, their mode of inflorescence, their dioecious flowers, also 

 in their floral and carpellary envelopes being charged with visciferous trachea?, and 

 in the form of the embryo, which is only partly immersed in the solid body of the 

 albumen. The structure of the anthers is likewise veiy peculiar ; in Viscum, these 

 are equal in size, and completely adnate to the segments of the perianth, and the 

 pollen is contained in a number of distinct cells arranged like a network over its 

 surface ; in Arceuthobium and in Myzodendron they are unilocular, bursting by a 

 small apical transverse fissure ; in Phoradendron they are 2-locular, discharging their 

 pollen by 2 apical pores, as in Choretrum, and the walls are thick and crustaceous. 



" Korthals first detected the fact of the existence of distinct ovules, suspended upon 

 a free central placenta, in the ovarium of two Javanese species, that he erroneously 

 referred to Tupeia, which he considered, on this account, to belong to Santalacese. 

 Mr. Brown was the foremost in pointing out the resemblance in this respect of the 

 structure of Myzodendron to the Santalacea?. M. Decaisne also confirmed the 

 existence of the same fact in the ovary of Viscum album, and this structure in 

 Myzodendron was beautifully illustrated by Dr. Hooker in his Flora Antarctica, 

 thus proving demonstratively the affinity of this genus towards the Santalaceae and 

 Olacacese : the embryo is there shown to be imbedded in a deep vacuity in the 

 summit of a large albuminous mass, and partly exserted and covered over by a thin 

 embryotega, or extension of the albumen (Plate 104, figs. 19 <£• 20). This the writer 

 of these notes finds conspicuous in Phoradendron, where the opercular membrane 

 bears considerable analogy with the singular mammiform protrusion seen in the 

 albumen of Commelyna and Tradescantia, called embryotega by Gaertner, and 

 operculum by Mirbel. We have sufficient evidence of the same structure in Viscum 

 album, from the clear details of the development of the seed and embryo, by 

 Richard, in Jussieu's memoir on that genus (Ann. Mus. XII., tab. 27). But notwith- 



Fig. DXXIV. quater. — Details of a Phoradendron. 1. fruit, witli half the calyx removed: 

 2. endocarp, with half the pericarp removed : :;. kernel, with naif the endocarp removed ; 4. upper 

 cud of kernel, showing the exserted embryo; 5. embryo separate. 



