RAFFLESIA: CUSCUTA : CASSYTHA 235 



to produce oxygen in light, but not to meet the constructive 

 requirements of the parasite. Cassytha is tropical : Ernst 

 (1908) describes it as growing in festoons on the strand 

 grasses of Krakatau. Cuscuta is widespread from the tropics 

 to the temperate zones, several species occurring in Britain. 

 Cuscuta Epithymum is common on whin, thyme, and 

 heather, Cuscuta Trifolii grows on clover, and Cuscuta 

 Epilinum on flax. 



The seed of Cuscuta germinates on the soil, usually, so 

 far as European species are concerned, late in the spring, 

 when other vegetation has sprouted, and young shoots of 

 host plants are therefore available. The late germination 

 may be determined by high temperature or light require- 

 ments. The root leaves the seed coat first and pushes 

 slightly into the soil, from which it absorbs water. 

 Cotyledons are absent or rudimentary. As the young 

 shoot, a fine yellow thread, grows, it appears to creep forward 

 on the soil. The tip is raised above the surface and cir- 

 cumnutates. If it fails immediately to meet a host it may 

 grow forward for some time at the expense of the basal 

 parts, which wither away,* but it ultimately dies. Spisar 

 (1910) found the maximum term of life without a host to be 

 seven weeks in Cuscuta Gronovii ; in smaller species it is less. 

 If it meets a living plant it commences to twine round it, 

 behaving in turn Hke a twining plant and like a tendril ; 

 that is, it alternates a series of loose elongated coils with a 

 series of close tight ones. Peirce (1894) agrees with older 

 investigators that the seedling dodder can only twine round 

 living plants, though the mature parasite can twine round 

 any support, living or dead. More recently, Mirande 

 (1900) and Spisar (1910) have found that the seedlings of 

 the small species, e.g. C. Epithymum, can twine round a 

 dead object if it is moist, while seedHngs of the large species, 

 e.g. C. Gronovii, can twine indifferently on wet or dry, dead 

 or living, supports. On the surface of the tight coils, in 

 contact with the host, epidermal adhesive discs, attached by 

 papillae which grow between the cells of the host, are formed 

 in response to the contact stimulus. The papillae also 



