184 BROOM-RAPES, BALANOPHOREiE, RAFFLESIACE^. 



one or other of these bends its tip towards the root of the foster-plant and clinga 

 to it. These fibres are, in many species, very numerous, and are interlaced and 

 entangled so as to form a reticulate mass, which vividly recalls that of the Bird's- 

 nest, and is an instance of the general resemblance existing between Orobanche^ 

 and the Orchidese destitute of green leaves {Neottia, Corallorhiza, Epipogum, 

 Limodoruvi), which have already been discussed. 



The establishment of parasitic Orobanche^ upon the roots of host-plants takes 

 place in the following manner. The embryo imbedded in the small seed shows no 

 trace of differentiation into root and stem, possesses no cotyledons, and indeed 

 consists only of a group of cells; it is surrounded by other cells filled with reserve- 

 nutriment. When this embryo grows forth from the seed, during which process it 

 consumes the reserve-food, it exhibits no distinction between root, stem, and leaf, 

 but is a spiral filament consisting of delicate cells. One extremity, the shoot end, 

 of this filiform seedling, remains covered by the seed-coat, which looks like a dark 

 cap (fig. 34^); the opposite extremity is the root. 



The seedling Broom-rape stretches downwards just as the Dodder (Guscuta) 

 extends upwards. In so doing the descending tip traces a spiral line, and so, 

 as it were, seeks in the earth for the root of a plant suitable as host. If the 

 search is fruitless, and if the reserve-material in the seed has meantime been 

 altogether consumed, the seedling begins to wither and gradually shrivels, turns 

 brown, and dries up. It lacks the power of nourishing itself by means of the 

 surrounding earth. But, if the lower, foraging extremity of the seedling succeeds 

 in finding a live root belonging to a plant able to serve as host, it not only adheres 

 closely to it, but swells in such a way as to give the young plantlet a flask-shaped 

 appearance (fig. 34' and fig. 34 1"). The upper end is still inclosed by the seed- 

 coat, but in proportion as the lower part thickens, the upper shrivels till no trace 

 of it is left. The thickened part, on the other hand, which has become attached 

 to the root of the host, becomes nodulated and papillose. Some of the papillae 

 develop into elongated conical pegs, and the young Broom-rape now rests upon the 

 nutrient root in the shape of the head of a fighting-club (see fig. 34 1^). At the 

 place of attachment one of the conical pegs has meanwhile penetrated the cortex of 

 the root, and there it continues to grow energetically, forcing the cortical tissue 

 apart, until it reaches the wood. Vessels now arise in the body of the young club- 

 like plant, and, passing through the middle of the plug, wedged in the nutrient 

 root, are brought into connection with the vessels of the latter. At the point of 

 union between host and parasite, a bud is formed, clothed with abundant scales, 

 which may best be likened to the bulb of the Martagon Lily. Lastly, out of 

 this bud grows a strong, thick stem, which breaks through the earth and lifts a 

 spike of fiowers into the sunlight. 



That portion of the Broom-rape which is buried in the root of the host-plant is so 

 intimately associated with the separate parts of that root in the development of a 

 tuber that it is usually diflScult to determine which cells belong to the parasite and 

 which to the host. The degree of union is such that one cannot even state with 



