OF BUCKLEYA QUADEIALA, B. EÏ II. 



21 



haustorium takes in its young- 

 est (I), middle (II), and oldest 

 stages (III) respectively. An 

 example of the quite similar 

 mode of the secondary growth 

 has already been civen by 

 Sachs with a similar diagram 

 of the wood of Aristolochia 

 Sipho, 2) where the inner an- 

 nual rings are at first ellip- 

 tical in cross-section, then circular and finally oval. He con- 

 cluded thereupon that the directions of the medullary rays are the 

 orthogonal trajectories of those of annual rings, so in our ease 

 the latter and the rows of vessels stand to each other in similar 

 relations. 



These morphological changes of the axial part during the 

 secondary growth take place also in its frontal part which lies in 

 the so-called sucker. The fact that the sucker, as has been 

 before stated, is primarily elliptically compressed along the axis 

 of the host, might be explained as the most suitable arrangement 

 for splitting the cortex of the host in order to make its way 

 easily into the wood 3) (Fig. 5. b, sue). 



The vigorous increment of elements only in the lateral direc- 

 tion during the secondary growth must also be considered as 



1). Sachs, Ueber Zellenanordnung und Wachsthum. Arb. d. But. Inst, in Wurzburg. 

 Ed. II, 1882, p. 192. 



2). Inc. cit. Fig. 3. 



3). If we take off the young Iiaustoria from the host spindle-shaped years will lie seen 

 on the central part of (lie contact surface. Heinricuer is of tin- same opinion as to the 

 reason why the tracheal plate in the sucker of Lathrœa is placed longitudinally (Anatomischer 

 Bau und Leistung der Saugorgane der Schuppenwurz-Arten. Cohn's Beitr. z. Biol. d. Pflz. 

 Bd. VII, 1896, p. 331). 



