PROCEEDINGS OF SOCIETIES. 343 
Huxley regarded as sporangia or spore-cases, and the smaller ones as 
spores, whilst he considered that their disintegration had led in most 
cases to the formation of the bu of what we call coal. Prof. Wil- 
liamson showed in detail that these were not spore-cases, but two 
s 
been deciduous organs. The lecturer then gave reasons for concluding 
i art in t igi 
vegetable tissue, but which, when their sections were examined under 
i ibi o trace whatever of organic structure, but 
of coal with few spores, and of spores without coal. Huxley 
concluded that coal osed . 0 ral arcoal and 
coal proper—the latter term being equivalent to spores altered 
or unalte e lecturer, on » her hand, ognised 
three such elements :—Mineral charcoal—7.e., fragments of fossil wood 
retaining its structure ; coal proper—?.é., mineral charcoal disorganised ; 
iou 
now distinguish three groups of fossil plants 
have the form, but not the organisation ; 2, those of which we have 
: 3 cipie' a 
y 
iart. trator supposed. 
These plants are chiefly Calamites, corresponding with living Horse- 
: Fy : 
circle of longitudinal woody wedges, the whole being encased 
thick bark. e When sand = mud entered the pith cavities 1t was 
pressed against the inner edges of the wedg y t 
the cast with longitudinal grooves, whilst a thick ring of pith remain- 
ing at each node occasioned trans : . 
The casts thus. moulded, and covered with a d 
only remnant of the original wood and bark, constitute 
