BROOM-RAPES, BALANOPHORE^E, RAFFLESIACE^E. 185 



certainty where the epidermis of the nutrient root ceases, and that of the Broom- 

 rape begins. The latter looks as if it were a branch growing out of the root it preys 

 upon, and this apparent fusion gave some colour to the view of the earlier botanists, 

 who, ignorant of the life-history of these parasites, believed that they did not arise 

 from seeds, but were pathological outgrowths of the roots, produced from their 

 tainted juices; in other words, that they were " pseudomorphs" sprouting from 

 diseased roots in the place of leafy branches. 



It is also deserving of mention that some of the thick, fleshy fibres issuing 

 laterally from the nodulated seedlings curve towards the host's root, bury their tips 

 in the cortex, and thenceforth behave exactly like the peg which was inserted at the 

 point where the seedling first became attached. We must leave undecided the 

 questions as to whether the other fibres, which terminate freely in the earth, are 

 capable of taking up food-materials from that source, whether these fibres are only 

 present in perennial species and become the starting-points of new individuals, and 

 lastly, whether they should be looked upon as root-structures or as stem-structures. 



In addition, it is noteworthy that in many Orobancheae only those embryos 

 continue to develop which meet with a plant suitable to be their host. Although it 

 is not the case that every species of Orobanche adopts one particular species of 

 plant as foster-parent, yet thus much is certain, that most of them only thrive on 

 members of a limited circle of species; one lives exclusively on kinds of Wormwood, 

 a second on species of Butter-bur, and a third on those of Germander. For 

 example, Orobanche Teucrii prevails on Teucrium Chamcedrys, Teucrium mon- 

 tanum, &c, the hosts being invariably species of the genus Teucrium. Suppose a 

 hill thickly covered with plants comprising Teucrium montanum growing in 

 company with thyme, rock-roses, globe-flowers, sedges, and grasses, but no great 

 abundance of the Teucrium, a plant belonging to the species named occurring only 

 here and there, and let Orobanche Teucrii have established itself at one particular 

 spot, have attained to flowering and developed fruits, the tiny seeds of which have 

 been shaken by the wind out of the ripe capsules. Owing to the exceptional 

 minuteness and lightness of its seeds, every gust of wind will scatter them in 

 innumerable quantities over the entire hillside and beyond it. The next step is 

 germination. Filiform embryos emerge from the seeds, in the manner described 

 above, and penetrate into the earth. Teucrium montanum being only sparsely 

 present on the hill in question, comparatively few seedlings will meet with the roots 

 of that plant, whereas thousands will fall in with the roots of the thymes, rock- 

 roses, globe-flowers, sedges, and grasses. But, curious to relate, only those seedlings 

 of Orobanche Teucrii which come into contact with the roots of Teucrium 

 montanum establish themselves firmly, penetrate into them, and continue their 

 development; whilst the numerous individuals which touch the roots of the thyme 

 and other plants perish. This phenomenon can scarcely be explained in any other 

 way than by the supposition that the roots of Teucrium montanum alone, by 

 virtue of their special structure and quality, afford a suitable nutrient substratum, 

 and therefore constitute centres of attraction for seedlings of Orobanche Teucrii; 



