Scrophulariaceae and Orobanchaceae 143 



Perhaps the most extensive morphological and physiological 

 studies of parasitic Scrophulariaceae and Orobanchaceae have 

 been made by Heinricher (7, p. 390-451, 665-773) and Solms- 

 Laubach (8, p. 560-75) on the former, by Beck (9, p. 7-70) and 

 Koch (10,) on the latter. The work on such genera as 

 Euphrasia, Odontites, Pedicularis and not least Bartsia and 

 Tozzia, by Heinricher has a very definite bearing on the present 

 investigation. To quote from him on Bartsia and Tozzia: "In 

 der That sind es diese beiden Rhinanthaceen, welche uns die 

 Briicke von den halbparasitischen Rhinanthaceen zu der holo- 

 parasitischen Gattung Lathraea bauen. . . . Der Aufbau 

 des Lathraea- Rhizoms ahnelt sehr dem von Bartsia, die Unter- 

 schiede sind wesentlich dadurch bedingt, das erstere H0I0-, 



letztere Hemiparasit ist Tozzia nimmt eine 



ganz eigene Stellung in der Rhinanthaceen-Rheihe ein; sie ist 

 nicht Holoparasit und nicht Hemiparasit, sondern sie ist beides 

 in zeitlicher Folge. Und so wird sie eben zum biologischen 

 Bindeglied Zwischen den Halbschmarotzern und der Holopara- 

 sitischen Gattung Lathraea. " 



In view of the above comparative estimates of different au- 

 thors, the question at issue resolves itself into one of three po- 

 sitions. (1) The Gesneraceae and Orobanchaceae are most 

 nearly related to each other in that they both possess a one-celled 

 ovary with deep to shallow parietal placentation. (2) Oro- 

 banchaceae and Scrophulariaceae are most nearly related to each 

 other in their root parasitism, their alternate or at times opposite 

 leaves, their progressive parasitic degradation, condensation of 

 axis, and eventually non-chlorophylloid aspect. They only 

 differ in the two-celled ovary, but Scrophulariaceae seem to be 

 united with Orobanchaceae by Christisonia neilgherrica, with 

 its two-celled, becoming above one-celled ovary, as well as by 

 Lathraea with its imperfectly two-celled ovary. (3) The Oro- 

 banchaceae stand by themselves as a family. 



To take the last caption first, Orobanchaceae being wholly 

 parasitic and non-chlorophylloid, clearly suggests that physiolog- 

 ically and now morphologically it is a degenerate offshoot from 

 some family that tended gradually to show semi-parasitic habit. 

 Now of all the Bilabiatae, there is only one other family which 

 shows, like Orobanchaceae, parasitic habits, namely, Scrophul- 

 ariaceae. No Gesneraceae are parasitic, or even show a slight 



