MICROSCOPIC OBJECTS. 81 



searches the different specimens must be ground into 

 thin laminae, so as to be viewed by transmitted light. In 

 some of Mr. Pritchard's preparations, these sections are 

 made in two directions, the one longitudinal and the 

 other transverse ; and by comparing them with similar 

 sections of recent coniferous woods their identity is esta- 

 bhshed. Among the ordinary Newcastle coal may often 

 be selected pieces indicating very clearly the remains of 

 woody fibre, and, more rarely, specimens occur in which 

 the vascular tissue is distinct, spiral vessels covering the 

 surface. Microscopic dra\vings of various specimens of 

 coal will be found in Mr. Witham's work on Fossil 

 Vegetables. 



Charcoal. — Thin transverse sections of charred woods 

 offer instructive examples of the formation of the different 

 layers, and for shallow powers or on the screen of the 

 solar microscope are beautiftd symmetrical objects. 



Ferns. — As microscopic objects the most curious and 

 interesting parts of the Fern are their reproductive 

 organs. By the ancients these plants were supposed to 

 be propagated by fairy hands. Swammerdam was the 

 first author who gave a drawing of them. The flowers 

 and seeds, or rather the parts which answer the purpose 

 of these, (for Ferns are considered by botanists both as 

 flowerless and seedless,) are small and hi3. on the back 

 of the leaves. They should be collected before they are 

 quite ripe. The spores (seeds) are usually inclosed in 

 rich brown capsules, each having an elastic ring about 

 its equator, which .when ripe bursts and the spores are 



