146 Boeshorer—The Morphological Continuity of 



gophylla with few pale green leaves and branches that mainly 

 carry on food elaboration, and finally to the most degraded mem- 

 ber, G aphylla, in which the leaves are small pale green scales, 

 still, however, provided with a few stomata, but which are in the 

 last stages of disappearance. It is of interest to note the close 

 resemblance in habit, structure, etc., between the two latter types 

 and such South African genera as Striga and Harveya, which 

 connect again with Hyobanche. All of these, but the last in par- 

 ticular, closely simulate members of the so-called Orobanchaceae. 

 Further, it is important to note that in the genus Christisonia 

 (Campbellia) , the ovary, while mainly one-celled with deep pla- 

 cental ledges, is in most of the nine species of Christisonia two- 

 celled in the lower part. And so Beck (12, p. 131) has well not- 

 ed, "Ausnahmsweise kammt bei letzterer ein unteren Teile 2 

 facheriger Frkn. vor; es besteht somit eine starke Annaherung 

 an die Gatt. Harveya." Regarding Christisonia neilgherrica 

 Worsdell (13, p. 131) says, "The ovary is bilocular in its lower 

 region and unilocular above; in the latter case the placentation 

 is parietal. In this plant the basal portions of the two bipart- 

 ite placentas very nearly meet in the centre. In the lower, bi- 

 locular part of the ovary, where the projections have become 

 united to form a dividing wall, the placentation is axile, two 

 placentas, bearing a large number of minute ovules, projecting 

 into each cavity." 



If the above morphological and physiological lines of con- 

 tinuity express a correct interpretation of the lines of evolution 

 pursued, it should be possible to trace certain fairly continuous 

 morphological similarities as well as degradation-differences, pro- 

 ceeding in relation to the following parts. 



First, since the phenomenon is fundamentally due to increas- 

 ing root parasitism, we should expect to find that the root and 

 gradually thereafter the vegetative stem system should show 

 condensation and swelling of the condensing axis, or, that this 

 axis should become rather starved and simplified. 



Second, in such condensed axes an increasing preponderance 

 in relative width and importance of phloem over xylem should 

 occur until in the most condensed genera it would become a pre- 

 ponderant feature. 



Third, in the above process and with the increasing parasitic 

 degradation the leaves would tend by degrees to become reduc- 



