BROOM-RAPES, BALANOPHORE^, RAFFLESIACE^. 183 



sented in fig. 37, is indigenous to Europe and Asia, its area of distribution extending 

 from England eastwards to the Himalayas, and from Sweden southwards to Sicily. 

 Two species are confined to the East, the Crimea and the Balkans, and another 

 Toothwort (Lathrcea clandestina), distinguished by large flowers, but slightly 

 raised above the earth, extends in western and southern Europe from Flanders over 

 France to Spain and Italy. This last has the distinctive feature that the discoid 

 suckers developed on its yellow roots, which latter are of the thickness of a quill, 

 are as large as lentils and the biggest hitherto discovered on any plant. 



BEOOM-RAPES, BALANOPHORE^, RAFFLESIACE^. 



The fourth series of parasitic Phanerogamia is composed of plants destitute of 

 chlorophyll, whose seed contains an amorphous embryo without cotyledons or 

 radicle. The seed germinates on the earth, and the embryo grows as a filiform body 

 into the ground and there fastens upon the root of a host-plant, penetrates into 

 and coalesces with it in growth, forming a tuberous stock, from which, later on, 

 flowering stems are projected above the earth. 



To this series belong the Broom-rapes or Orobancheae and the Balanophoreae. 

 Of the genus Orobanche about 180 species are recognized, which, exhibiting great 

 uniformity in floral structure and in their general development, can only be 

 distinguished by minute characteristics. The flowering stem growing up from the 

 subterranean tuber is, in all the species, rigid, erect, thick, fleshy, and covered at the 

 top with dry scales. The open flowers, ringent in shape, are crowded together in a 

 terminal spike, and often emit a strong scent like that of pinks or sometimes of 

 violets. The colour of the flowers is in one group (Phelypcea) mostly blue or violet; 

 in the rest it is waxen yellow, yellowish-brown, dark-brown, rose-red, flesh-tint, or 

 whitish. Orobanche violacea and 0. lutea, both natives of Northern Africa, have 

 stems which grov/ to a height of half a meter and become almost as thick as an arm. 

 The best-known species is the Branched Broom-rape (Orobanche ramosa), which is 

 parasitic on the roots of hemp and tobacco plants, and is very widely distributed. 

 The greatest number of species belong to the East and to Southern Europe. The 

 extreme north of America harbours one species which bears a single flower at the 

 end of its stem. In all the species the stem projects only partially above the earth. 

 The subterranean portion, adherent to the root of a host, is often greatly swollen 

 and thickened above the place of attachment; in the case of Striga orobanchoides, 

 which is prevalent in the Nile basin, it is irregularly lobed above the host's root. 

 The root of the nutrient plant also is usually somewhat swollen wherever a 

 parasitic Orobanche has settled upon it, and sometimes it exhibits an irregular 

 outgrowth inclosing the spot whereto the Orobanche is adnate like a cup. Beyond 

 the place of attachment of the parasite the root has often the appearance of having 

 been bitten oflf, and this is owing to the fact that the particular piece of root has 

 been killed and demolished by the attack of the parasite. From the base of the 

 stem, near the point of adhesion to the host, spring short, thick, fleshy fibres, and 



