62 
Peirce. — A Contribution to the 
three centimetres long and another one millimetre long. By 
the great range of curves which these parasites can make, they 
are enabled to conform themselves to the most variously- 
shaped parts of their hosts. 
Another quality of the host must now be considered, how- 
ever. If the first plant about which a seedling of C. glomerata 
lays its coils be an Impatiens of one of the three species 
mentioned above, the haustoria will penetrate easily and find 
abundant nourishment. But if the seedling fastens itself upon 
some other plant its chances may not be so good. If the 
plant be a hard and comparatively innutritious Grass, or 
a tolerably woody herb or shrub, the haustoria will penetrate 
more slowly and will secure less nourishment, and hence the 
parasite will not so soon be able to develop its stem and 
branches, or so abundantly. Thus its chances of quickly 
finding a more nutritious host are lessened. The success of 
the Cuscuta , its dangerousness as a parasite, depend in the first 
place upon the number of seeds each plant forms, upon the 
distribution of these in places where many herbaceous plants 
grow close together, where the ground is moist, or where the 
abundance of larger herbs form a covering under which 
a moist atmosphere is confined, and hence where transpiration 
is not excessive. 
2. Conditions necessaiy for the formation and development 
of haustoria. 
The quickly-growing main stem and branches enable the 
young parasite to reach out in many directions, to lay hold 
upon the branches of its host, upon other plants, and indeed 
upon all objects which can mechanically support it, be they 
wet or dry, smooth or rough, living or dead. When the 
plant has secured a suitable host and has entered upon the 
period of healthy activity which an abundant supply of 
food ensures, it is in the most suitable condition for 
experiment. 
After a period of short close winding about a host, a period 
