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IX. 



SELF-PAEASITISM OF CUSCUTA REFLEXA. Br 

 HEIs^EY H. DIXO^, D.Sc. 



[COMMUXICATED BY PROFESSOR E. P. -WRIGHT, M.D.] 



[Read December 12, 1898.] 



So far as I know, cases of a parasite sending haustoria into tlie tissues 

 of its own branclies have not been previously recorded. Peirce,^ 

 indeed, states that he has looked for such cases in Cuscuta, but has 

 failed to find them, and concludes that it is improbable they occur. 



Some three years ago I happened to cut sections of the branches 

 of a specimen of C. reflexa twining on Cofoneaster micropTiylla. I 

 noticed that in several places haustoria were developed, connecting 

 one branch of the parasite with another. At the time I thought that 

 the development of cork on the surface of the Cotoneaster prevented 

 the penetration of haustoria into it ; and that the Cuscuta, unable to 

 support the two branches which were climbing on the host, was 

 utilizing the haustoria to transfer all the available material from one 

 branch to the other, concentrating, as it were, all its resoui'ces in the 

 maintenance of one branch. 



Recently, however, cases were found from the same material which 

 do not bear out this explanation. Thus, in many instances, the parasite 

 did actually penetrate into the tissues of the stem of Cotoneaster, and 

 specimens were obtained showing that where two branches of the 

 Cuscuta twine on the host, one may simultaneously send haustoria 

 into the Cotoneaster and into its own neighbouring branch. The 

 distance between the two haustoria was in some cases less than one 

 millimetre. Similar examples were found where two branches 

 twined on Hedera helix. 



These observations would seem to show that the self-parasitism is 

 not dependent on the stimulus of starvation. For in the cases men- 

 tioned the parasite was actually simultaneously drawing on the 

 supplies offered by its host, and maintaining connexion with its own 

 branch. 



What determines which of the two intertwining branches of the 

 parasite shall form the haustoria seems hard to discover ; structurally 



1 " Annals of Botany," 1893, p. 291. 



