6 DR. J. D. HOOKER ON THE STRUCTURE AND 
Two forms of attachment are found amongst the genera with branched and much- 
-elongated rhizomes. In Helosis the rhizome forms a tuber at each point of its attachment 
to the various roots it meets with in its subterranean course, and a few vascular bundles 
from the root are rarely sent into it at these points; but these do not appear to commu- 
nicate directly with the previously existing vascular tissue of the rhizome, nor to become 
blended with it: possibly, however, they may have been given off by it, or have been 
independently formed in the rhizome; a point which can only be determined by exami- 
ning the nature of the attachment at its first formation, and which I shall hereafter 
discuss. In Langsdorffia the branch of the rhizome corrodes the bark of the roots it 
encounters; the first contact in the case of L. rubiginosa being by means of woolly hairs. 
Both the rhizome and the root generally swell considerably, but often do not, and the 
root sends long vascular branches, apparently covered with the cellular bark of the root, 
right and left into the axis of the rhizome; with whose vascular system, however, I have 
never found them to form an organic adhesion (see Plate IT. figs. 10, 12, 13, 16, 17). In 
this genus two or more species of dicotyledonous plants sometimes send their roots into 
one tuber of an old rhizome, each penetrating at several points. 
In the Annals of the Vienna Museum (ii. 53), I find Balanophoree arranged by Unger 
under three of the divisions, into which all parasites are separated by that author according 
to the nature of their parasitism ; they are the following :—1. Parasites which form a _ 
rhizome by which they adhere to the roots of plants, and from which the flower-buds rise. _ 
Example, Scybalium. 2. Parasites which exercise a powerful specific action upon the root, 
causing it to send vascular bundles into the rhizome, which hence becomes an organ in- 
termediate in nature between the stock and the parasite. Examples, Balanophora, Sarco- 
phyte, Cynomorium, Lophophytum ? Ombrophytum ? 3. Parasites which form a rhizome 
intimately attached by its vascular tissue to the root. Examples, Helosis, Langsdorffia. — 
It appears to me that the above are rather distinctions of words than of facts; and that — 
in so far as they are correct, any one of the three definitions is more or less applicable to 
all the species : for all form rhizomes, all owe their adhesion to their power of exerting à 
specific action upon the roots from which they derive their nourishment, and except inthe 
case of Lophophytum (and perhaps of Ombrophytum, which I assume to. have the same 
mode of parasitism as Lophophytum), all more or less present the appearance of the vas- 
cular bundles of the root being enclosed in the cellular tissue of the parasite. Further, if 
my observations are correct, both Helosis and Langsdorffia should be transferred to the 
first class; for there is certainly no distinct union of their vascular bundles with those of 
the root, nor do their rhizomes appear to send any bundles towards the root; on the 
contrary, the appearance is perfectly distinct of the root sending its branches into the 
on Langsdorffia indeed is described both by Richard and (apparently following 
a 5 ling forth root-fibres from its rhizome ; but I not only fail to discover 
ok ES : e very numerous specimens I have examined, but I find this appearance 
produced by fibres being given off from the roots of the plant on which the parasite 
grows, which fibres become included within the rhizome (Plate II. fig. 11) 
The differences therefore that prevail amongst the modes of parasitism of Balanophoreæ, 
are of degree only: the power of erosion and of forming an organic adhesion is the main 
