104 Henderson — Comparative Study of Pyrolaceae and 



leaves from evergreen leathery in Ericaceae, Chimaphila, and 

 some of the Pyrolas, to less leathery in P. chlorantha and P. 

 minor, to evergreen leaves but with deciduous structure in 

 Moneses, to scales which are brownish (Pterospora), brownish 

 yellow or yellow (M. hypopitys), red {Sarcodes), brownish white 

 (Pleuricospora) , to white (M '. uniflora) . This is correlated with 

 the gradual increase in size and persistence of the scales from 

 green or brownish in the Ericaceae to herbaceous, persistent, 

 but still small in the Pyrolaceae, to large fleshy and colored in 

 the Monotropaceae. Stoma ta are very numerous on the leaves 

 in the Ericaceae, become less numerous in the Pyrolaceae, very 

 few in the scales of Monotropa and Pterospora and absent entirely 

 in those of Sarcodes. All of these changes are correlated with 

 increasing saprophytism. 



The inflorescence is a raceme or condensed to a corymb, or 

 solitary in each of the three families. The sepals are green, 

 united, in the Ericaceae and Pyrolaceae; brownish, united, in 

 Pterospora; red, very slightly united, in Sarcodes; becoming 

 separate, yellow, in M. hypopitys; and white in M. uniflora. 

 The petals are 5-4, separate, to united shallow campanulate, 

 to campanulate, to irregular campanulate, to urceolate in the 

 Ericaceae; there are five separate expanded, to separate cam- 

 panulate in the Pyrolaceae; to separate campanulate in Mono- 

 tropa; to united campanulate in Sarcodes; to urceolate in Ptero- 

 spora. Stamens are generally twice the number of petals in 

 the Ericaceae, and always so in the Pyrolaceae and the Mono- 

 tropaceae. They bear two horns in many of the Ericaceae and 

 Pyrolaceae. They are awned in the urceolate corolla types in 

 the Ericaceae and in Pterospora (which has an urceolate corolla) 

 of the Monotropaceae. The dehiscence is apical porous, longi- 

 tudinal, or transverse in the Ericaceae, apical porous in the 

 Pyrolaceae; and apical porous, longitudinal, or transverse in 

 the Monotropaceae. Pollen grains occur in tetrads in all of 

 the Ericaceae and all of the Pyrolaceae except P. secunda. In 

 P. secunda and all of the Monotropaceae they are simple. 



In the Ericaceae, the ovary is completely 5-4-celled. In 

 the Pyrolaceae, in the upper half of the ovary the placentae fail 

 to meet and fuse. They almost meet, so that the ovary is 

 practically five-celled. In the Monotropaceae, there is a gradual 

 decrease in the length of the placental in-growths to Pleuri- 



