Johnson . — On A rceuthobinm Oxycedri. 157 
live organs by Solms-Laubach 1 is exhaustive. The course 
and structure of the vascular bundles are described and figured 
by Chatin 2 . Objection to the course of the bundles described 
by Chatin is taken by Solms-Laubach, who points out that 
this observer has overlooked the two small lateral vascular 
bundles in the scaly vegetative leaves. The extremly com- 
plicated system of intra-cortical mycelioid branching haustoria 
is shown by Solms-Laubach to be deducible from the 
single primary haustorium of the Santalaceae, just as is the 
case in the other less modified Loranthaceae examined by him. 
The modification wrought by parasitism in Arceuthobium has 
not proceeded pari passu in the vegetative and sexual 
organs. Its intra-matrical vegetative organs present an ex- 
treme of modification, whilst its gynaeceum is much less affected 
than that of most other Loranthaceae. I could not find 
any purely vegetative specimens in the crowded adventitious 
extra-cortical shoots. The connection between the xylem- 
elements of the parasite and those of the host is easily 
observed. The radial wall of the xylem-tracheide of the 
host is split along the middle lamella, so that the fine 
secondary haustorium with its thin wall has only half the 
thickness of the tracheide-wall on each side intervening 
between it and the cavity of the tracheide. 
The germination of Arceuthobium is unknown. I found one 
or two ejected seeds on pieces of the host-branch, and in one 
the radicle showed a distinct curve towards the host-branch, 
so that Arceuthobium is probably in its hypocotyledonary 
stem negatively heliotropic, and in its root independent of 
geotropism like Viscum album. 
Of the thirteen species mentioned by Eichler 3 only five or 
six are regarded as good in the Genera Plantarum of Bentham 
and Hooker, and of these A. Oxycedri is the most widely 
1 Solms-Laubach, Ueb. d. Ban u. d. Entwick. d. Ernahrungs organ e parasit. 
Phanerog, in Pringsheim’s Jahrbiicher, vi. 1867, p. 615. 
Solms-Laubach, Das Haustorium d. Loranthaceae, etc., in Abh. d. Naturf. 
Gesell. zu Halle, xiii. 1875, p. 256. 
2 Chatin, Anat. Comp. d. Vegetaux, Paris, 1856-1862, p. 484, PL Ixvii. 
3 Eichler, FI. Brasil. V, Pars 2, p. 105. 
