56 DR. J. D. HOOKER ON THE GENERA AND SPECIES 
perianthii breviter bilabiato coronatum, 1- (rarius 2-3) loculare. Styli 2, rariüs plures, filiformes, 
Stigmata subcapitata, papillosa. Ovulum 1, pendulum. Fructus subcrustaceus. Semen 1, achenio 
conforme, testá tenuissimá hyaliná reticulatá. 
Helosis appears to be the commonest American genus of the Order, inhabiting both — 
sides of the Andes, and extending from Mexico to the river la Plata. The species much 4 
resemble one another in general characters, and are of a whitish colour tinged with red, 
and become red-brown when dry: they are said to inhabit moist grounds, where their 
rhizomes spread annually by innovations to a considerable distance, seeking nourishment 
from various roots in their progress, and seeming to have the power of attacking such as 
they come in contact with. Each year’s rhizome is probably annual, and it gives off an 2 
innovation before dying, as described by Richard; the whole mass sometimes perishes … 
at once. 
The parasitism is simply that of adhesion by the contact of the tissues of the Helosis 
with those of the root-stock ; in the older specimens there are no vascular bundles uniting 
both, and the roots attacked do not swell up to any remarkable size at the point of union; 
though the parasite often penetrates deeply into the wood by a conical protuberance. In 
very young plants, however, the wood of the root-stock ramifies extensively through the 
tubers of the parasite. A transverse section of the rhizome shows a most distinctly | 
exogenous structure, very curiously modified, and varying considerably in the different — 3 
species, under which the details will be given which have been already referred to in the | 
general remarks on the anatomy of the Order. å 4 
The peduncles are always erect, and rise from a swelling on the rhizome, whence they — 
receive many vascular bundles. The bundles in the peduncle are, however, simple, and 4 
either promiscuously scattered, or arranged in a circle; each resembles in structure that : 
of a monocotyledonous stem, having its own liber, wood, and vascular portions; but the E 
bundles do not follow the course that they do in endogenous stems, and are not to be — 
regarded as indicating any affinity between Helosis and Monocotyledons: they are, in 
fact, solitary bundles such as occur in the leaves, and often in the annual flowering | 
branches of other Exogens. E å = 
An incomplete involucre, generally divided into 3-6 broadly ovate segments, is frequently 
present in this genus; in H. Guyanensis it is placed at the base of the peduncle, in the 
Andes variety of that species it is carried up towards the apex, while in H. Mexicana it 
is either reduced to an elevated ridge round the centre, or entirely absent. When fully 
developed, this involuere never encloses the young capitulum. : 
Se peltate, fleshy scales cover the whole capitulum, as in the Indian Rhopa- 
48. na very young state these will be found to be developed as imbricating, 
ascending, bracteal leaves, each covering a definite portion of the inflorescence, which is 
indicated by a vascular bundle, given off from a plexus in the bod 
thei en. À y of the capitulum; 
_ their position is hence analogous to bracts subtending branches of a flowering axis. As 
the inflorescence grows, they become peltate, hexagonal from mutual pressure, and ad- 
hering by their contiguous edges, fall away i : 
R , y in large masses, 1 ; 
faintly marked on the capitulum, : 18» PaVIDG corresponding areola 
The male flowers haye usually a conical body at the base of the tube of the perianth, 
