Monotropaceae with Reference to Ericaceae 75 



which live above ground only one season, there is no separa- 

 tion of the cortex even suggested. Pterospora is reported by 

 MacDougal to have the epidermis and the two outer layers of 

 the cortex slightly lignified, but in the others the cells are not 

 at all thickened. 



The structure of the axis also illustrates a gradual descend- 

 ing series from typical Ericaceae, with strong development of 

 wood, to Chimaphila, which is almost as woody as some of the 

 sub-shrubby Ericaceae, to Pyrola, which is less woody, to Mon- 

 eses, with still less wood developed, then with a still decreasing 

 amount of wood development through Pleuricospora, Sarcodes, 

 Pterospora, and finally to Monotropa, where the wood is ex- 

 tremely small in quantity and the phloem well developed. 



The Leaf 



In C. umbellata the stem produces above ground alternating 

 groups of 2-3 scale leaves and whorls of 3-5 foliage leaves. 

 The leaves persist for four years. The last whorl of leaves 

 and the inflorescence appear in the same year so that no scale 

 leaves occur between the youngest whorl of leaves and the 

 inflorescence. The leaves are leathery, somewhat narrow at 

 the base, becoming wider above with a serrate margin, dark 

 green above, lighter below. 



In C. maculata, there is the same alternating arrangement 

 of scales and leaves as in C. umbellata, except that only three or 

 four foliage leaves are produced in a whorl. The inflorescence 

 does not appear in the same year as the last whorl of leaves as in 

 C. umbellata, so that above these at the base of the flowers talk 

 three scales are borne. These are the scales which protected 

 the inflorescence over the preceding winter. The leaves are 

 leathery, lanceolate, with an acute apex, serrate, dark green 

 above (though lighter than in C. umbellata), with white spots 

 especially along its midrib, and rather reddish green beneath. 



In P. rotundifolia, the arrangement of scales and leaves is 

 like that in Chimaphila, except that one to three foliage leaves 

 may be produced in one year, and that these are not arranged 

 in a whorl as in Chimaphila. The leaves are evergreen, lasting 

 from two to four years, and the node between two successive 

 years leaves is short, so that the leaves of two to three years 

 appear to be in a common rosette. They have long, narrowly 



