6o 
Peirce . — A Contribution to the 
enables the young plant to increase considerably in diameter 
where it has twined (an increase in size like that well known 
in tendrils 1 ), to form haustoria, to develop the tabular 
epidermal cells overlying the nascent haustoria into long 
papillate cells, such as I have already described 2 , and whose 
special functions I shall presently discuss. During the process 
of winding about the host, growth in length becomes slower, 
and finally almost, if not altogether, ceases, while the plant is 
increasing in diameter, forming haustoria, and sending them 
into the host. The haustoria having penetrated by the means 
which I shall describe later on, and having united their 
phloem- and xylem-elements with the phloem- and xylem- 
elements of the vascular bundles of the host, as I have 
described in the preceding paper 3 , the young Cuscuta now 
receives an abundant supply of food. Much of this food it 
accumulates in solid form before it begins to grow again 
in length, as the abundance of starch-grains in the cortex 
indicates. When considerable quantities of reserve material 
have been thus accumulated, the plant, now entirely parasitic, 
grows for a time very rapidly, not only the main stem 
increasing in length but one or more buds, found generally 
two or three together in the axils of the small scales which 
are the only leaves that the plant has, rapidly develop 
into branches whose number, length, and thickness are pro- 
portional to the number of haustoria which the Cuscuta 
has been able to form, and upon the nutritiveness of 
the host. 
The age and size of the host at the point where it is attacked 
greatly influence the parasite. If the host be of consider- 
able diameter, two centimetres for example, the seedling will 
usually fail to effect a single turn about it : or if it be one-and- 
a-half centimetres, the parasite can make only one turn, and 
thus will not clasp firmly enough to enable many haustoria to 
penetrate ; hence the supply of food obtained will not be 
1 Darwin, C., Movements and Habits of Climbing Plants. 
2 Peirce, G. J., loc. cit. 
3 Id., loc. cit., p. 295. 
