174 ON CUSCUTA GRONOVII. 



dodder — further than to obtain a few coils about the stem. We 

 never suspected the unsuitable character of the hosts, as out-door 

 dodders do not seem particular. But an enterprising seedling 

 taught us the lesson by seizing a young geranium petiole, just 

 emerging from the bud, and beginning to grow by feet in the 

 same pot where a Eupatorium-entertained companion, of the same 

 age, grew scaly, stubby, and by inches, and all others died. After 

 this there was no difficulty in raising dodders. 



The suckers are, outwardly, enlarged fleshy discs, which the 

 parasite forms and presses hard against the host, sending into it 

 from their centre, filamentous organs called haustoria, by which 

 they absorb the elaborated juices as roots take moisture from the 

 soil. They differ from true roots, as does the root-acting end of the 

 stem, in the absence of a root-cap. 



An attempt to remove the dodder from a stem to which it is 

 well attached often ends in taking with it at least the cortex of the 

 plant on which it grows. Sections either longitudinal or vertical 

 through the parasite, in position on its host, median as regards a 

 sucker, will explain this. Each sucker starts, as does a root, in 

 the vascular tissue of the stem, and is a cylinder, sharpened like a 

 blunt pencil, where it enters the host and enlarges immediately 

 afterward. Thus is made a sort of neck about which the epider- 

 mis of both host and parasite fit very nearly ; the sudden 

 enlargement of the latter, in its new quarters, serving, as does a 

 nut on a bolt, to prevent its easy removal. 



The suckers, in their origin, are domes of meristem tissue 

 before they reach the epidermis. Whatever lack of discernment 

 the dodder may show in its selection of a host, once well placed, 

 it lives up to its opportunities. It may, and usually does, in a 

 woody stem like that of Solidago, send one root into the centre, as 

 if for deep anchorage, but spreads out by far the larger portion of 

 its absorbing tissue in the cambium and sieve-tube regions, where 

 elaborated material is most abundant. Its tissue is easily dis- 

 tinguished from that of the host by its enlarged thin-walled cells 

 with prominent nuclei. When the cutting was exactly median, the 

 tissue seemed like a compact cylinder made up of filaments of 

 cells, end to end, like meristem tissue, which branched, however, 

 in a variety of ways inside the host. When growing on hollow 



