Monotropaceae with Reference to Ericaceae 97 



The pollen grains of Ericaceae always occur in tetrads. This 

 is true also of the Pyrolaceae except for P. secunda. This 

 species forms a transition to the Monotropaceae where all the 

 pollen grains are single. 



The Pistil 



In C. umbellata, the ovary is somewhat flattened-globose, 

 with its outer surface ridged from the anthers being pressed up 

 against it. The outer surface is covered with simple papillar 

 hairs. It is completely five-celled, with a central placenta at 

 the base, but the upper half is one-celled through the failure 

 of the bilobed parietal placentae to meet and fuse in the center. 

 The space between the placentae is, however, very small, so 

 that it appears more like a five-celled ovary than a one-celled 

 one. The placentae bear numerous anatropous ovules. The 

 style is short, top-shaped. The stigma is broad and five-crenate, 

 with a disc-shaped border. At the base of the ovary is a circular 

 disc which secretes nectar. 



In C. maculata, the ovary is similar to that of C. umbellata, 

 the outer surface being ridged from the anthers, but no hairs 

 are present. The number of cells, etc., is the same as in C. 

 umbellata. The nectariferous disc is present, similar to that 

 of C. umbellata. The style, however, is slightly longer; the 

 five stigmatic lobes protrude slightly more from the disc. 



In P. rotundifolia, the ovary is five-lobed, with glabrous 

 outer walls. The same transition from a five- to a one-celled 

 state occurs, as in Chimaphila, this being characteristic of the 

 family. No nectariferous disc is present. The style is long 

 declined, with the apex turned upward. . The stigma consists 

 of five narrow, erect lobes, which extend out from the top of the 

 style that forms a rim beneath the stigmatic lobes. 



In P. elliptica, the ovary and style are similar to those of 

 P. rotundifolia. No nectariferous disc is present. The lobes 

 of the stigma are however slightly longer, and the rim at the 

 tip of the style greater in diameter than in P. rotundifolia. 



In P. secunda the ovary is five-lobed, subglobose, with ten 

 small nectariferous lobes at the base. The ovary is five-celled 

 for most of the distance; the region where the placentae fail to 

 meet is limited because of the deep insertion of the style. This 

 is erect, straight, exserted, about 4 mm. in length. The stigma 

 is peltate, much broader than the style, with five diverging lobes. 



