ON CUSCUTA GROXOVII. 



175 



stems like grasses, as it was common to find them, the haustorium 

 scarcely branched, there being little opportunity. 



One of the most singular phases of dodder life was a sort of 

 self-grafting or self-parasitism. With a low power it was difficult 

 to distinguish which was host and which guest, as the haustorium 

 extended from the vascular region of one stem to the same of 

 another. In examining the alcoholic specimens, I found this 

 common, and it has often been repeated on those growing in my 

 own room, usually under such circumstances as these : If a 

 parasite had occasion to twine about an already thickly covered 

 host, in its anxiety to obtain its share of elaborated material, it was 

 willing to take a sort of second mortgage upon it, after it had 

 passed into the tissues of the first; this inter-parasitism also 

 occurs frequently when for a long distance stems intertwine. 



There is little differentiation in the tissues of the dodder ; it 

 needs, very early, conducting tissue for carrying moisture through 

 the stem to the rapidly growing and probably assimilating apex. 

 To meet this need, vascular tissue is found as soon as germination 

 takes place. It is very simple, consisting of alternate stripes of 

 tracheids and parenchyma, each about two rows of cells broad, 

 and in the best developed stems occupies perhaps from one-third 

 to one-half the diameter. It is well adapted for twining by this 

 alternation with the softer parts, while the predominance of the 

 latter favours the carrying of elaborated material, as it is in these 

 such products travel. Iodine testifies to the presence of starch 

 in the tissues of mature plants. Other re-agents show, as do the 

 markings on the walls, the woody nature of the alternate bands 

 evident in a section of stem. 



Of the adventitious buds, known to be abundant in the 

 dodders, I have studied only those producing branches. 



Their origin was in this manner : When a parasitic root had 

 become well established, so that the plant was thoroughly 

 engrafted upon the host, in an axil thus formed, a branch would 

 arise, after the manner of an axillary branch on a normal plant. 

 The regular branching of a stem of Cuscuta is unusual in the 

 centrifugally arrangeda ccessory buds (Figs. 6 and 7), the last- 

 formed bud being farthest from the parent stem, though sections 

 show it to originate in the axil bundle. 



