254 



ABSORBING SYSTEM 



studied in detail by Solms-Laubach, L. Koch, Heinricher and others, 

 may be discussed somewhat more fully. 



Thesium proteose (Santalaceae) is a parasitic herb, the roots of 

 which produce peculiar haustorial organs in the shape of ovoid or 

 almost campanulate outgrowths (Fig. 100 a). According to Schwarz, 

 the young haustorium attaches itself to the surface of a host-root by 

 means of root-hairs. When fully developed, the " apex of the haus- 

 torium sits upon the root, just like a saddle on a horse's back." In a 

 longitudinal section the haustorium is seen to consist of an axile 

 portion surrounded by a sheath of cortical tissue. The former, which 



Fir.. 100. 



Haustorimn of Thesium pratense. A. Section through the root of the (Dicoty- 

 ledonous) host and a haustorium of the parasite, slightly magnified ; root (w) in T.S., 

 haustorium in L.S. ; s, haustorial process. B. Portion of a L.S. through the root and 

 the haustorial process, x80 ; the elongated absorbing cells of the latter are arranged 

 in a fan-shaped manner. After Solms-Laubach. 



may be termed the " haustorial core," is more or less flask-shaped. 

 " The ovoid belly of the flask is completely invested by the cortical 

 tissue of the haustorium ; a conical process, which corresponds to the 

 neck, projects into the tissues of the host-root, far beyond the surface 

 of attachment." This haustorial process {Saugfortsatz) is the only part 

 of the organ that interests us at present, since it is there that the 

 whole of the absorbing tissue of the parasite is located. It consists 

 mainly of elongated parenchymatous cells rich in protoplasm, but also 

 contains two vascular bundles which are crescentic in transverse section. 

 The terminal cells of this process, which constitute the actual absorbing 

 tissue, are distinguished by their greater length ; their tips are rounded 

 or club-shaped, and are closely apposed, either to extracambial cells of 

 the host-root, or to elements of the woody cylinder. These terminal 



