& 



174 CLIMBING PARASITES. GREEN-LEAVED PARASITES. TOOTHWORT. 



tered, lying on the damp eai'th i'or four or five weeks waiting for something to 

 turn up. Not infrequently something of the sort happens, for another plant may 

 germinate close by or extend a gi-owing shoot from the vicinity and touch the 

 Cuscuta seedling. In this event, the latter at once seizes the anchor thus tlirown 

 out, and winds round it. But if no support of the kind is to be had, the seedling 

 must ultimately perish. It is, to say the least, a very remarkable thing that a 

 filament, capable of developing suckers when adherent to a living plant, is not able 

 in damp eai'th to pi'oduce any absorbent organs whatsoever. 



If the thread-like Dodder plantlet succeeds in seizing a support of any kind, 

 either during the existence of the swollen extremity, or later, after it has been 

 absorbed, it makes a single, or from two to three, coils round the prop, raises its 

 growing point from the sulistratum, and moves it round in a circle like the hand 

 of a watch. By means of these manoeuvres, which look exactly like a process 

 of feeling or seeking, the filament is brought into contact with fresh haulms, 

 twigs, and petioles belonging to other plants. To these it adheres, making once 

 more two or three tight coils round them. Throughout, it is obvnous that the 

 growing point of the young Dodder rejects dead props, as far as is practicable, 

 and shows a striking preference for living parts of plants. 



At each place where the Dodder is pressed in a coil against the support, the 

 filament becomes somewhat swollen, and wart-like suckers are developed, which are 

 usually situated close together in rows of three, four, or five (see fig. 35 ^). 



A piece of stem thus furnished with suckers or haustoria resembles a small 

 caterjjillar creeping up the supporting stem. These haustoria, arranged close 

 together in rows, and corresponding in origin entirely to rudimentary roots, are at 

 first smooth, but acquire soon a finely -granulated aspect owing to the walls of the 

 epidermal cells projecting outwards. With the help of the papillae thus formed, 

 and especially through the action of a juice secreted by them, the suckers fasten 

 themselves to the host. If the plant has been obliged to clasp a dead object for 

 support, the wart-like processes flatten themselves against it and assume the form 

 of a kind of disc, which exhibits no further development, and only serves as an 

 organ of attachment; but, if the substratum is a living plant, a bundle of cells 

 forces its way out from the middle of the haustorium and grows into the sub- 

 stratum direct. The phenomenon here manifested is altogether characteristic. 

 Each sucker from the time of its production exhibits a kind of core composed of 

 cells arranged in regular rows, which, together with a few spirallj^-thickened 

 vessels, constitute a bundle standing at right angles to the axis of the Dodder's 

 stem. This bundle now breaks through the coat formed by the rest of the cells 

 of the sucker and penetrates into the living tissue of the plant attacked (see fig. 

 35°). Great force is exerted in the penetrating process. The closelj* -joined cells 

 of the epidermis, and not infrequently a cortex of considerable density are pierced, 

 and tlie bundle of cells often penetrates right into the body of the wood. Having 

 once reached the interior of the host, the cells, till then bound together in a 

 bundle, diverge a little, insert themselves singly between the cells of the host, 



