Weiss . — A Mycorkiza from the Lower Coal-Measures. 257 
a similar specimen from the collection of the late Mr. James Spencer, of 
Halifax, which he had purchased some years ago. It turned out to be 
undoubtedly of the same nature as the specimens in the Cash Collection, 
and is in all probability from the same locality, as most of Mr. Spencer’s 
material came from the Halifax Hard Bed. 
The Host Plant. 
The only remains that we have of the host plant are a few delicate 
root-like organs ranging from about 1 to 2 mm. in thickness. In all the 
specimens so far discovered the tissues are well preserved in comparison 
with the surrounding plant-remains, which have for the most part under- 
gone considerable destructive changes. Among the debris are seen spore- 
cases, apparently of a fungal nature, and numerous opaque, rounded masses 
(see PL XVIII, Fig. 1), which are generally taken to be excrements of wood- 
boring animals. The whole has the aspect of a mass of humus in which 
Fungi and animal organisms were causing a gradual breaking-down of the 
vegetable remains. Only a few hard macrospores, some Stigmarian rootlets, 
and the mycorhiza in question seem unaltered — a fact which is suggestive of 
their having grown in the humus-like mass. 
The internal structure of the mycorhiza at once suggests a root of the 
diarch type, but differs in several respects from other diarch roots found 
among Coal Measure plants. It should be added that these root-like 
remains are very constant in character, and therefore easily recognizable. 
As seen in PI. XVIII. Fig. 1, the root has two groups of wood distinctly 
separated by well-marked ground-tissue cells. These are present in all the 
specimens, and as the larger ones are evidently mature we may consider that 
the xylem-rays did not meet in the adult organ, as is generally the case in the 
roots of Ferns. In a smaller specimen than that in Fig. 1 these medullary 
cells are filled with curious granules (PI. XVIII, Fig. 2, and Text-fig. 42), the 
nature of which is uncertain. At first sight they closely resemble a number 
of starch-grains, but it is somewhat doubtful whether starch would be pre- 
served with quite so definite an outer boundary. On the other hand, they 
do not seem in any way connected with the Fungus, which does not as a rule 
penetrate to such depths ; nor does the Fungus in other parts of the plant, 
where it occurs, produce granules quite of this kind. It would, therefore, 
seem more probable that the granules are the normal cell-contents at 
a certain stage in the development of the organ or under certain conditions 
of nutrition. 
With regard to the xylem-groups, it is not always easy, or indeed 
possible, to distinguish the protoxylem-elements. In Fig. 2 the smaller 
elements seem to be on the outside of the wood ; but, as will be seen from 
Fig. 1, this is not always the case. In one group, indeed, the smaller 
elements appear to be on the inside. Their position is in fact irregular, and 
