32 ART. 10. S. TCUSANO : STUDIES ON THE PARASITISM 



7. The Connection of the Haustorium with 

 the Mother-Root. 



The final point in the structure of the haustorium, to which 

 I wish to refer, concerns the connection of the haustorium with 

 the mother-root. This was omitted in the description of the 

 young haustorium, as I deemed it better to study the point on 

 the haustorium which had already undergone the secondary growth. 

 To begin with the wood of the mother-root, it is composed 

 of pitted vessels, wood-parenchyma and thin-walled wood-fibres, 

 traversed by medullary rays with lignified walls. At the place 

 where the haustorium occurs, vessels are exceedingly numerous 

 and some of them are directed towards the haustorium as a 

 massive strand of reticulated vessels, which, after passing a certain 

 distance, comes in contact with the bottom of the vascular strand 

 of the haustorium (Fig. 7 ne). This part which thus connects 

 the haustorium with the mother-root, is called the neck of the 

 haustorium. In the median portion of the neck the vessels are 

 exceedingly small in number, mostly forming isolated chains of 

 vessels among the parenchyma, The longitudinal and cross 

 sections reveal very clearly the course of the vessels in this region 

 (Fig. 12). 



In a section taken near the mother-root the vessels are 

 arranged compactly in radial rows (Fig. 19 a) ; and again near 

 the bottom of the vascular strand they unite and fuse together 

 into those of the strand. 15 



1). A similar structure was ascertained in Lathrcea by Heinricher. He says (Cohn's 

 Beitr. loc. cit. p. 334): "Die Tracheen verlaufen in derselben in bogigen Curven, welche 

 mehr minder senkrecht an die Tracheen des Wurzelstranges ansetzen, da und dort finden 

 sich zwischen den Tracheen nocli paronehymatisehe Elemente eingeschaltet." (Compai-e bis 

 illustration, Taf. VII, Fig. 2). In the young haustorium of Buckleya, in which the develop- 



