202 T. Holm — North American Terrestrial Orchidem. 



6 short, but broad groups of rather narrow vessels, alternating 

 with a corresponding number of small groups of leptome, 

 while a pith occupies the greater inner portion of the central- 

 cylinder. 



Calypso borealis Salisb. 



The structure of the root is almost identical with that of the 

 preceding, and the only differences observed were as follows : 

 the hypoderm is very distinct and the cell-walls are slightly 

 thickened ; the cortical parenchyma is a little broader and 

 quite open, the intercellular spaces being relatively wide ; the 

 hadrome occurs only as small, 3 to 6, groups of vessels, alter- 

 nating with the leptome and separated from the center by a 

 large mass of thin -walled pith. 



Goodyera pubescens R. Br., repens R. Br., Menziesii Lindl. and 

 tesselatum Lodd. 



In respect to the root-structure these species resemble each 

 other very much, and we find in these the same delicate struc- 

 ture of the various tissues, as described above as characteristic 

 of Arethusa and Calypso. The roots are very hairy, the 

 epidermis, the hypoderm, the cortex, the endodermis and the 

 continuous pericambium are all thin-walled ; of these, the cortex 

 consists of about 6 layers in G. repens and tesselatum, of 8 in 

 G. pubescens, and of about 12 in G. Menziesii; it is quite 

 compact in all the species except in G. tesselatum, in which 

 the intercellular spaces are much wider than in the other 

 species. The hadrome and leptome constitute small groups, 

 when viewed in transverse sections, the former with 4 to 8 

 vessels in each group, widely separated from the center of the 

 cylinder by a large, starch-bearing and thin-walled pith. The 

 number of hadromatic groups is somewhat variable within the 

 species examined ; thus 4 were observed to be characteristic of 

 G. repens, 5 of G. tesselatum and 6 of the other species. No 

 hyphse were found in the internal tissues of G. repens or G. 

 tesselatum, but in the cortex of the others. 



Chlorcea Austinm Gray.* 



Although the roots of this plant are relatively strong, much 

 more so than in any of the other Orchideai described above, 

 the structure does not reveal any very pronounced mechanical 



* The statement by Mr. MacDougal (Bull. Torrey Club 26 : 528, 1899) that 

 " this plant is to be added to the list of chlorophylless plants furnished with 

 stomata" is not correct, since we have observed the presence of chlorophyll- 

 grains in the ovary ; the guard-cells of the stomata as well as the adjoining 

 epidermis-cells are well supplied with chlorophyll. The description and the 

 figures furnished by this author (1. c.) are altogether very inexact. 



