140 Boeshore — The Morphological Continuity of 



Introduction 



In the past, the genera of Orobanchaceae have been regarded 

 as of nearest affinities with the Gesneraceae; this wholly because 

 of the one-celled ovary. But such a proceeding only takes ac- 

 count of one morphological detail. Is there any other family 

 with which Orobanchaceae can be directly and continuously 

 connected in many morphological features? The group, being 

 wholly parasitic, must of necessity be derived as an offshoot from 

 some family wholly free or more or less parasitic in habit. 



The only related family showing such is Scrophulariaceae. 

 While the majority of these in genera are green and independent 

 in their nutrition, others show all stages in degradation-transi- 

 tions to reduced green root parasites, thence to yellowish, or 

 red-yellow parasites, finally to degraded simplified parasites 

 that are wholly heterotrophic (Harveya, Hyobanche) . Thus, for 

 example, in the single genus Gerardia of the Eastern United 

 States some species are tall leafy plants, as in G. flava, and these 

 show slight root parasitism. Transitions can be traced from 

 this to G. pedicularia, thence to G. purpurea, to G. oligophylla, 

 and to G. aphylla, the last of which has scant twigs and small 

 leaves that may be almost absorbed. The flowers in the latter 

 are few and reduced in size, while parasitism is almost complete- 

 ly established in relation to other plants. From such forms 

 transition is easy and gradual to Striga, Harveya, and Hyobanche. 

 But between Harveya and G. aphylla on the one hand, or species 

 of Orobanche on the other, the macroscopic and microscopic 

 resemblances, as will afterward be shown in this paper, are grad- 

 ed and complete. Is then the fundamental resemblance to 

 Gesneraceae of a one-celled ovary as compared with Scrophular- 

 iaceae with its two-celled ovary fundamental and indicative of 

 true affinity? This question will be fully worked out in a later 

 part of the paper. But attention might now be drawn to .ome 

 comparative morphological facts that may shed light on the 

 present problem. 



If we review the more pronounced saprophytic families of 

 flowering plants, like Burmanniaceae, Orchidaceae, Ericaceae, 

 (including Monotropaceae) and Gentianaceae, all show degra- 



