Monotropaceae with Reference to Ericaceae 53 



In Monotropa there is a similar mass of roots. The main 

 root is thick, horizontal, giving rise to inflorescence buds and 

 to secondary roots, which are short, fleshy, and intertwine 

 closely to form a compact mass. Drude (11), Kamienski (39), 

 Queva (62) call this horizontal structure a root. Peklo (59) 

 calls it a "Rhizomaste." The structure is so simplified that 

 it is difficult to determine whether it is a root or a rhizome. 



There is therefore in the underground root and stem system 

 a gradual condensation and simplification from genera like 

 Chimaphila and Pyrola, which have, as in certain typical Erica- 

 ceae, extensively branching rhizomes from which are produced 

 the vegetative axes as branches in the axils of scales, to Moneses, 

 where the rhizome is completely lacking and the vegetative 

 axes arise endogenously from an old horizontal root which 

 closely resembles a rhizome in appearance; to Pterospora, Sar- 

 codes, and Monotropa, where the horizontal root has become 

 very much condensed, thickened, and fleshy, also producing 

 vegetative buds endogenously. The roots, from being thin, 

 wiry, and sparsely branching in Chimaphila and Pyrola, have 

 the primary root enlarged and thickened in Moneses, Pterospora, 

 Sarcodes, and Monotropa. The secondary roots begin to show 

 a slight swelling at the tip in P. rotundifolia and P. elliptica. 

 This swelling becomes greater, secondary roots become short- 

 ened, thickened, and more fleshy and much more numerous, 

 so that there is a close compact mass of roots in Pterospora, 

 Sarcodes, and Monotropa. 



The Root 



In Chimaphila umbellata, sections of the root tip (fig. 1, 1) 

 show a short root cap of 4-5 layers at the very tip. This to- 

 gether with the epidermis arises from a common tissue, there 

 being only three regions of growth, the calyptro-dermatogen, 

 the periblem, and the plerome. The epidermal cells at the tip 

 are small, indistinguishable in size from the others, but soon 

 show gradual increase in size, particularly in a radial direction — 

 the radial width becoming three to four times the length. This 

 gradual increase occurs under the root cap, this region never 

 being infested by fungi. Above the root cap, the cells suddenly 

 become larger and square in section. These cells are infested 



