374 AMERICAN JOURNAL OF BOTANY [Vol. 9, 
capsules in line with projections of the pedicels, and Plagiothalamium, 
having them turned downwards at right angles to the pedicels. 
Fig. 4. Marcgravia purpurea spec. nov. Mature inflorescence. Four calyptriform 
corollas removed to show stamens. X i/i. Drawn from material preserved in formalin- 
alcohol by Miss Grace Griftin. 
It is evident, accordingly, in viewing the Marcgraviaceae as a whole, 
that there are certain distinct and closely correlated lines of morphological 
specialization which reach their climax in Plagiothalamium. In this sub- 
genus the racemes are compacted into pendulous umbels, the large, highly 
modified nectariferous bracts are terminally segregated and are adnate 
to sterile pedicels, the corolla is fused into a deciduous capsule or thalamus, 
and the flower buds are bent downwards at right angles to the pedicels. 
Significance of Floral Morphology of Marcgraviaceae 
Delpino (1869), who devoted considerable attention to the Marcgra- 
viaceae, believed that the nectariferous bracts function as attracting organs 
in connection with the cross-pollination of the protandrous flowers; the 
small nectaries providing food for insects, and the larger and more complex 
