174 Boeshore — The Morphological Continuity of 



often a median knob in line with the antero-posterior axis of the 

 flower, or somewhat displaced. 



1 1 . Evidence has been given to show that while the ovary is 

 two-celled in Scrophulariaceae and usually one-celled with deep 

 to shallow placentas in Orobanchaceae, all transitions between 

 these can be traced from Harvey a and Hyobanche to Lathraea 

 clandestine and Christisonia albida, etc. 



12. As to seeds, these are few (4-12) and fairly large in the 

 less parasitic Scrophulariaceae, becoming decidedly small and 

 numerous in Harveya and allied types of Scrophulariaceae as 

 well as in all of the Orobanchaceae. 



13. In structural details and morphological complexity the 

 seeds show continuous degradation changes from the less para- 

 sitic genera of Scrophulariaceae to the most degraded genera of 

 Orobanchaceae, such as Aphyilon and Conopholis, in which a 

 rudimentary endosperm and formless embryo are alone devel- 

 oped up to the time of germination. 



14. Physiologically it has been shown that in transition from 

 the less parasitic Scrophulariaceae, like Odontites and Gerardia 

 which parasitize on a variety of hosts, transitions are shown to 

 genera like Orobanche, some species of which seem to confine 

 their parasitism to the species of a family or even to the species 

 of a genus, as pointed out by Beck (p. 31), while finally in such 

 a highly degraded type as Epiphegus abundant evidence shows 

 it to be purely parasitic on Fagus americana, Aphyilon to be 

 similarly wholly parasitic on Aster corymbosum, and Conopholis 

 on one or two species of Quercus. 



Conclusions 



From a review of the above observations, the writer believes 

 that ample evidence has been adduced to show that direct and 

 distinct continuity can be established from non-parasitic through 

 semi-parasitic Scrophulariaceae to the most degraded parasites 

 of the family, and that these again show direct continuity with 

 the still more degraded and condensedly parasitic types of Oro- 

 banchaceae. 



Alike logically and biologically, therefore, the two types 

 should be treated in continuous descending series from the high- 

 est to the most degraded genera. 



