The Microscope, 299 



be of such a consistency that when applied to the surface of 

 paraffin it will dry in two or three seconds. This has no tend- 

 ency to cause the sections to roll. As soon as the collodion is 

 dry, . . . cut the section, withdraw the knife, and pass the 

 coUodionized brush over the newly-cut surface of paraffin." The 

 section is placed collodion side down on the slide. The sections 

 are fastened by placing a little clove oil collodion on the slide 

 and placing them in it, and evaporating the clove oil. They are 

 placed on the slide in series and in definite order, and are then 

 washed in xylol for ten minutes or more. This removes the 

 paraffin. Then they are washed in alcohol, afterwards with 

 water, ai;d stained. I have found no stain as good as hsema- 

 tox^din for this work. They should be stained with it for from 

 three to five minutes. After the washing with water, dehydrate 

 with alcohol, and clear. Three parts turpentine and two parts 

 carbolic acid make a very good clearing mixture. Canada bal- 

 sam dissolved in xylol is used for mounting. 



In sections thus prepared, one can distinguish without diffi- 

 culty in shepherd's purse, golden rod, or any endospermous 

 seed, the coats, the plumule, composed, as is the lower tip of the 

 radicle, of small thin-walled cells, bearing nuclei. These two 

 regions of growth are connected by slightly elongated cells 

 which are also thin walled. The larger cells making up the 

 tissue of the cotyledons are stored with food. In many seeds a 

 trace of a vascular system may also be seen ; also the peculiar 

 arrangement and markings of the cells composing the coats. 



Seeds differ so much that one would need to make many vari- 

 tions in method to suit special cases, but as a general plan I 

 have found this to be a success, and I believe the histology of 

 any seed may be demonstrated by it. 



THE OBJECTIVE AS A SUB-STAGE CONDENSER. 



PROF. WM. LIGHTON. 



SOME time ago I carried on a series of experiments in illumin. 

 ating microscopic objects when using high power objec- 

 tives, and was greatly interested in one which yielded a remark- 

 ably crisp and vigorous image of the object under examination. 

 My object was mounted between two very thin cover glasses, 



