234 THE BIOLOGY OF FLOWERING PLANTS 



That of the Javan Rafflesia Arnoldi, blood-red in colour, 

 stinking like carrion, and measuring a yard across, is the 

 largest known flower. Cytinus has short fleshy scapes with 

 several flowers, the brilliant yellow of which, contrasting 

 with the equally brilliant scarlet of the scaly bracts, makes 

 them lovely objects as they appear above the bare brown soil 

 below the Cistus bushes of the garigue. The flowers or 

 inflorescences of the Rafflesiaceas spring straight from the 

 cortex of the host plants. When they break through the 

 cortex of a stem, e.g. Pilostyles on vines, they present a very 

 remarkable sight, the trunk of the host appearing to blossom. 

 The vegetative body exists entirely inside the host. In 

 most cases it is reduced to an irregular weft of branching 

 filaments, which wander through the parenchymatous 

 tissues of the host. In Cytinus and some others undiffer- 

 entiated strands of tissue are formed. The inflorescence 

 starts as a parenchymatous swelling inside which a vegetative 

 point is ultimately laid down ; this gives rise to the bud 

 which breaks through the tissues of parasite and host to the 

 exterior. 



In the Rafllesiacese we have the ultimate stage of reduc- 

 tion of the vegetative body, which is at a level of organisa- 

 tion no higher than that of a fungus. Of the flowering 

 plant structure the flower alone remains, and \\e may note 

 that the seeds are minute, the embryo is undifferentiated, 

 and the development of the gametophyte is abnormal. 



Cassytha and Cuscuta. — The two isolated parasitic 

 genera Cassytha and Cuscuta, differ widely from other 

 parasites. They possess extensive branching stems which 

 twine round the stems and leaves of the hosts. The leaves 

 are reduced to minute scales ; chlorophyll is often present, 

 but usually in such small amount that the plant appears 

 quite yellow. Cassytha, according to Mirande (1905), 

 has abundant chlorophyll. It is capable of slow growth 

 for as much as eight months without a host, but develops 

 rapidly only when it has attached itself to another plant. 

 Some dodders, e.g. the tropical Cuscuta reflexa, are markedly 

 green. Photosynthesis may in these be sufficiently vigorous 



