604 Osborn— Lateral Roots of Amyelon radicans , Will., 
investigation is principally based are: A 275, 281, 282, 283# and ser., 
in Mr. Watson’s collection, and R 707, 716 in the Manchester Museum. 
I have also to thank Dr. Smith Woodward, Keeper of the Geological 
Department, British Museum (Nat. Hist.) for facilities to examine the 
Williamson Collection, in which I found numbers 931 and 932 to be 
specially useful. 
In spite of the common occurrence of mycorhiza amongst recent plants, 
only one case has been recorded from the Coal Measures. In 1902 
Professor Weiss ( 21 ) described from this laboratory a small rhizome that 
appears to have had an undoubted mycorhizic habit. The material in this 
case was a petrifaction from the Halifax Hard Bed, which is renowned for 
the beauty of its preservations. In this respect he was more fortunate than 
I have been in the material here used. All the slides examined in this 
investigation have been cut from material from Shore or Oldham, at which 
places Amyelon is particularly abundant. Though the preservation of cell- 
structure is excellent, the detail in many cases is necessarily not so clear, 
owing to the contents being of the same brownish colour as the cell-walls. 
In spite of this difficulty it has been possible to make out an abundant 
occurrence of hyphae in some of the cells. 
An examination of an unthickened and uncrushed rootlet (PI. XLVI, 
Fig. 2), which may be as much as 1-5 mm. in diameter, shows a wide 
cortex, consisting of two well-defined zones. The outer cortex is of 
parenchymatous cells, often of small radial diameter. In some specimens an 
epidermis appears to be distinguishable by its more distinct outer wall, 
and the more regular shape of the cells. The cells of this outer region are 
elongate in longitudinal section, and are almost without exception void of 
contents, so that it is clearly distinguishable from the succeeding zone. In 
the inner cortex the cells are also of thin-walled parenchyma, larger than 
those of the preceding region, and irregularly hexagonal in transverse 
section. They are somewhat elongate when seen longitudinally. In contra- 
distinction to the cells of the outer cortex, the cells here frequently have 
a dark cell contents. In some cases this occupies the whole cell, though in 
others it appears to have contracted towards the walls, or to form a more or 
less central mass with connecting strands to the walls. These masses 
of cell contents are apparently tangled knots of fungal hyphae filling the 
entire cell. In those cases where the contents are contracted, the hyphae 
appear to have been absorbed by the host plant, the indigestible residue 
being left. Such is usually the case with recent plants, and has been noted 
by Weiss for Mycorhizonium. 
Some cells appear to be perfectly empty, though well preserved, as 
if the fungus had not affected them in any way. This invasion of certain 
cells and omission of others by the symbiotic fungus has been commented 
upon by Groom ( 3 ) in Thismia Aseroe . 
