OF BUCKLEY A QUADKIALA, B. ET H. ( .> 



terminal one. Such is the case when the axis both of the haus- 

 torium 13 and the mother-root run in the same direction, while the 

 mother-root grows in thickness together with the haustorium, the 

 thickening taking place gradually towards the haustorium (Fig. 

 4. b). The root thus thickened looks as if its tip, in the course 

 of its longitudinal growth penetrated into another root, or as if its 

 tip expands after it has come in contact with the root. Even 

 where the haustorium is terminal, the exact limit between it and 

 the mother-root is clearly distinguishable, if the mother-root be 

 slender and the haustorium greatly developed, or if the direction 

 of the axis of the mother-root be at a right angle or nearly so 

 to that of the haustorium, as it should be if the haustorium were 

 originally in a lateral position (Figs. 3 ; 5. c). 



TV. ANATOMY OF THE HAUSTORIUM! 



Let us now turn to the discussion of the inner structure of 

 the haustorium. This is in general so similar to that of the 

 Sanlalaeea' already investigated that it seems scarcely worth while 

 to enter into details. But as the structure varies within certain 

 limits according to age, it deserves special attention as to its 

 modification. For the sake of convenience I shall discuss the 

 structure of the young and old specimens separately. I shall 

 first take up the young stage in order to show how closely the 

 structure of the haustorium in this stage resembles that of other 

 Santalacese in the main, endeavouring at the same time to make 

 intelligible its later modification as well as the nature of some of 

 its tissues, which have hitherto been misunderstood. 



1). By the axis of the haustorium is meant that line which connects its point of origin 

 and the front of the haustorium. 



