296 Dr. Falconer on Gamoplexis. 



on parasitical plants, affirms that no true instance of parasitical growth occurs 

 among the Monocotyledones. 



I have described the ovarium as consisting of six pieces, such being the 

 apparent condition of the organ, without reference to any theoretical views 

 regarding its numerical composition. Ordinarily, in the Orchidece the pla- 

 centiferous portions of the valves are brought more or less into apposition by 

 their margins, which are overlapped by the costse. In Gamoplexis the costal 

 segments do not overlap, but are interposed between the placentiferous pieces, 

 and in form they differ from the latter only in being narrower, and this in a 

 less degree than is usual in the order. 



Dr. Lindley, the latest systematic writer on the Orchidece, comprises the 

 genera allied to Gastrodia in a section of the tribe Arethusece ; but the cha- 

 racters of the pollen-masses composed of largish angular lobules, and the 

 basal stigma, together with the habit, seem sufficient to entitle them to the 

 rank of a distinct tribe, as first suggested by Mr. R. Brown in his ' Prodro- 

 mus.' The Arethusece, as now constituted by Dr. Lindley, appear to include 

 a very heterogeneous assemblage of genera. 



EXPLANATION OF TAB. XIII. 



Fig. 1. A plant of Gamoplexis orobanchoides, reduced to half its natural size. 



Fig. 2. A flower of the same. 



Fig. 3. The tube of the perianthium slit open, and showing, a. the labellum ; b. b. the lateral 



segments of the inner series ; and c. c. c. the three segments of the outer series ; 



all cohering. 

 Fig. 4. The column seen on its labellar face, showing the stigma and fallen pollen-grains. 

 Fig. 5. The column, seen laterally. 



