T. Holm — North American Terrestrial Orchidem. 199 



moderately thickened in G. guttatum. The cortical parenchyma 

 consists of from 6 to 8 strata with large deposes of starch ; it 

 is quite compact, but thin-walled, except in G. puhescens, where 

 the cell-walls are thickened and porose. Endodermis is mostly 

 thickened as an U-endodermis outside the leptome, but it is 

 otherwise thin-walled, and the following deviations may be 

 mentioned. In G. acaule, guttatum and arietinum 3 to 4 

 thick-walled cells were observed outside the leptome, while 6 

 in G. Galifornicum; in G. pubescens and G. montanum 2 to 4 

 cells were thickened like an O-endodermis outside the leptome, 

 while in G. fasciadatum the entire endodermis was found to 

 be thin-walled throughout. The pericambium is only repre- 

 sented by a single continuous layer in all the species; it is 

 thin-walled except in G. arietinum. The rays of the hadrome 

 are very broad and meet in the center ; they average from 5 to 

 10, 8 to 10 being the characteristic of G. montanum • a thick- 

 walled pith forms a small central group in G. Galifornicum, 

 but not in the others. The leptome is well developed in large 

 groups alternating with the rays of the hadrome. 



JSTone of the roots were found to be contractile, and hyphag 

 were noticed in : G. pubescens (epidermis, hypoderm and cor- 

 tex), G. fascicidatum (cortex) and G. guttatum (endodermis 

 and pericambium). 



Epipaciis gigantea Dougl. 



Epidermis, hypoderm and cortex are all thin-walled, and 

 much starch is deposited in the cortical parenchyma. The 

 endodermis is thin-walled throughout with the Casparyan spots 

 plainly visible and with contents of starch ; the pericambium 

 forms a closed ring around the leptome and hadrome ; it con- 

 sists of only one layer, the cells of which are prominently 

 thickened outside the leptome, but otherwise thin-walled. Five 

 broad rays of hadrome extend to the center of the cylinder and 

 alternate with large, roundish groups of leptome. ^N"o hyphse 

 were observed. 



Lister a cor data R. Br. and L. austrcdis Lindl. 



The structure of the roots of these two species is almost 

 identical, and the difference depends merely upon the relative 

 development of hairs, which are very numerous and long in 

 the former species, but quite scarce in the latter; moreover, 

 the leptome constitutes groups of quite large dimensions in 

 L. cordata, but not in the other species ; otherwise the struc- 

 ture is identical. Epidermis and hypoderm are thin-walled, 

 and the cortex which occupies the greater portion of the root 

 is composed of about 5 layers, the cells of which are very large, 

 thin-walled and filled with starch ; the intercellular spaces are 



