172 BRITISH LICHENS. 



These various devices of nature presented to us in the structure of 

 the apothecium of Lichens are directed towards one object — the develop- 

 ment, protection, maturing, and dispersing those important bodies, the 

 spores. As we have before hinted, these bodies being regarded as the 

 female organs, we must now turn our attention to the organs designed 

 for their fertilisation. These are believed to exist in the Spermagonia and 

 the Pycnides, which shall now be briefly described. 



The spermagonia are mmute spherical bodies found on the surface 

 of or embedded in, the cortical layer of the thallus. If one of these be care- 

 fully dissected through the middle it will be found to have its interior 

 lined with excessively minute thread-shaped jointed upright bodies, (Fig. 

 14c,) which are called sterigmata. From the summits, and also from the 

 joints of these arise still smaller, rod-like cylindrical bodies, which are 

 either straight or curved, these are the spermatia. They are produced in 

 great numbers, and find their way through an opening in the summit of 

 the spermagonium into the open air to perform their function of fertilising 

 the hymenium of the apothecium. 



The pycnides are minute dark-coloured bodies somewhat spherical in 

 form, seated on the cortical layer of the thallus, the interior of which is 

 lined with a layer of simple upright filaments bearing on their summits 

 spore-like bodies, which are called stylospores, (Fig. 15, a, b, c.) The fila- 

 ments bearing the stylospores are called basidia. The stylospores are 

 allowed to escape by a pore in the summit of the pycnides. We have now 

 completed the drier part of our subject, not without regretting that 

 so many hard names have had to be used to convey our meaning, the 

 acquirement of a knowledge of which is the tax we all have to pay on 

 entering the domain of science. Once acquired, however, they become 

 our greatest aids to study, and lead to a precision of thought which more 

 familiar but ill-defined terms would utterly fail in. Leaving this thought 

 to console the student for his trouble, we will now turn to easier branches 

 of our subject. 



(To be continued.) 



FOSSIL FISH REMAINS FROM THE CARBONIFEROUS 

 LIMESTONE OF SOUTH DERBYSHIRE.* 



BY E. WILSON, F.G.S. 



At Ticknall, the most westerly of eight small inliers of Carboniferous 

 Limestone, on the borders of Derbyshire and Leicestershire, the highest 

 beds of the limestone series are well exposed in the extensive quarries 

 on the estate of Sir John Harpur Crewe, Bart., at the east end of the 

 village of that name. The sections in these rocks here show about 

 twenty-five feet of interstratified blue fossiliferous limestones and shales, 

 capped by about fifteen feet of reddish yellow dolomitic limestone. 



* Read before the Natural Science Section of the Nottingham Literary ar:d 

 Philosophical Society, 2nd May, 1879. 



