—— 
PO Te 
es a he 
* * 
wy oy Sy all a il Sh os I er ce a 
= . : ¢ 
of the Orobanchacex. 31 
of the roots arise from the bundles of the tuber and are of the 
reticulated kind; the cortical layer of the roots is continuous 
with the cortical parenchyma of the tuber. 
These tubers of Orobanche propagate by subterraneous buds. 
It is well known that the plants often occur three or four ad- 
hering together, but I believe the reason has not before been 
shown. I found growing plants with the decayed tubers of the 
preceding year still adherent, and others which had completed 
their flowering, that had buds growing out from the base of 
the tuber. These buds were not axillary in appearance, for they 
arose quite below the lowest scales of the tuber, but it is reason- 
able to suppose that they had originated from the axils of scales 
which had decayed. 
The most important point remains, viz. the mode of attachment 
of the parasite to the foster-plant. I have only observed this in 
O. minor ; here the root of the Trifolium was traced into the sub- 
stance of the tuber ; its fibro-vascular structures become sepa- 
rated, and lose themselves by ramifying im the substance of the 
parasite. The union is completely organic, and in one speci- 
_ men examined the tuber had grown so much that the root of the 
Trifolium, which was curved round the tuber, lay imbedded in 
a groove formed by the growth of the latter, but actual union 
only existed at the apex of the root which penetrated into the 
substance of the tuber. 
The point which has always struck me most in observing the 
parasitism of Orobanche is the small size of the root to which 
they are always attached, and it appears to me that there is much 
yet to be explained both in this tribe and in all the other root 
parasites. ‘The presence of proper roots would seem to indicate 
that the parasites are not wholly nourished from the foster-plant, 
a conclusion which irresistibly presses upon us when we see a tall 
Orobanche some two feet high and three-quarters of an inch thick 
attached to a slender root not measuring a quarter of an inch 
in diameter. Their own proper roots in Orobanche are small and 
_ few in number, and I believe that in O. rapum at least, the whole 
tuber with its scales is an absorbing organ. My reason for this 
supposition is the condition of its tissues. The tuber and scales 
are composed almost wholly of succulent cellular tissue ; the epi- 
dermis resembles the epithelium of roots, and like it dries up and 
becomes discoloured very rapidly on exposure to the air. These 
structures are manifestly as well adapted to the absorption of 
fluid nourishment as the aérial roots of the epiphytic Orchi- 
daceze, and I see no objection to the assumption that they are so 
employed. 
The question of the parasitism is not interfered with by the 
above proposition ; but we have to account for the assimilation of 
