808 



greatest care. The very brittle roots of the Thesium itself, and the 

 closely interwoven roots of the many plants which compose the turf 

 of the chalk hills, render the extrication of a perfect specimen a la- 

 bour requiring no small degree of patience. The root of Thesium, 

 after descending into the turf for about an inch, becomes repeatedly 

 divided, and spreads for many inches in various directions. It is 

 nearly white, and thus contrasts strongly with the dark epidermis of the 

 roots of the generality of its supporters. On coming in contact vv'ith 

 the root of its future support, the root of Thesium produces a hemi- 

 spherical tubercle, which firmly fixes itself; while from its centre pro- 

 trudes a tongue-like process (spongiole), which penetrates into the 

 very heart of its supporter, often causing very considerable derange- 

 ment in its tissues. After the perfection of the first tubercle, the root 

 is continued from the side of the tubercle, so as to give it the appear- 

 ance of having been formed laterally, and proceeds at greater or less 

 intervals to form more tubercles in the same manner on the same or 

 neighbouring roots. On the larger roots of its supporters it is not 

 usual to find more than one or two tubercles ; and these are mostly 

 large : the largest I have seen being about the eighth of an inch in 

 diameter ; but on the fibrous roots of grasses and other small plants 

 they are very small, and may be fi-equently found succeeding each 

 other so quickly as to resemble a string of beads. 



" Like Cuscuta, our species of Thesium appears to be by no means 

 particular in the selection of its supporters ; and I have ascertained 

 its attachment to the roots of the following plants, namely, Anthyllis 

 vulneraria, Thymus Serpyllum,. Lotus corniculatus, Daucus Carota, 

 Scabiosa succisa, Carex glauca, and some grasses. It is probable 

 that a single plant of Thesium subsists, at the same time, on the roots 

 of the whole of the plants above enumerated. 



" Through the kindness of Mr. Borrer I have been able to examine 

 the specimens published in Reichenbach's 'Flora Exsiccata ;' and I 

 find the roots of Thesium alpinum {Linn.), T. ebracteatum [Hayne), 

 T. rostratum {Koch), and T. liuophyllum [Linn.), to have precisely 

 the same structure as that of our own species. Unfortunately the 

 roots of the other species contained in this collection were too imper- 

 fect to afford any information ; but from the very close relationship 

 of all the European species, there is good ground to infer that they 

 are all of the same parasitical nature." 



