TWENTY-THIBD ANNUAL MEETING. 



163 



THE UNION OF CUSCUTA GLOMERATA WITH ITS HOST. 



W. O. STEVENS, LAWBENOE. 



In Hanstein's botanische Abhandlungen, vol. II., 1875, Koch figures one species 

 of Cuscuta, probably C. epilinum, as connected with its host by means of a rootlet 

 -which is prolonged into numerous well-defined hairs. By means of these hairs the 

 needed food is absorbed from the host. 



The parasitic roots, or haustoria of Cuscuta glomerata, somewhat common with 

 us on Solidago and other compositje, present some striking differences. A longi- 

 iudinal section through the slender stem of this species reveals no bundles of bast 

 or wood, nor the variously marked ducts so common in most plants. In their place 

 are tracheids fitfully distributed. The remainder of the stem is evidently paren- 

 chymous tissue. 



The parasite twines closely about its host and sends off haustoria at short inter- 





liongltudinal section showing the fusion of the tracheids of Cuscuta glomerata with the ducts of Soli- 

 dago. 



vals. The haustoria are formed by the rapid division of the parenchymous cells 

 probably at those points where the irritation from pressure is greatest. The tra- 

 cheids are formed early in the growing tissue. The haustorium bursts through its 

 epidermis, and if in a favorable place, enters its host. Sometimes it is unable to do 

 this, and spreads out as an external disk. If successful in entering the host, it 

 spreads out through the cortical parenchyma, passes between the bast bundles, and 

 to and through the bundles of wood and ducts. Often the tracheids of the haustorium 

 are turned aside when they reach the ducts, becoming closely applied to them for 

 some distance, and apparently fusing with them. The parenchyma of the hausto- 

 rium becomes lost in the parenchyma of the cortex, so that it would be difficult to 

 tell how far the haustorium extended, but for the tracheids which appear here and 

 there. 



