THE MICROSCOPE IN HISTOLOGY AND BOTANY. 153 



views of other observers may be verified, or additions 

 made to our knowledge of vegetable life. 



The lower forms of algae and fungi, to which we have 

 already referred, need scarcely any preparation, save the 

 disentanglement of twisted threads under the simple mi- 

 croscope, or a gentle teasing with needles, or rinsing with 

 water. The solution of iodine, and of iodine and sulphuric 

 acid, will suffice to exhibit the nature of the cell-wall and 

 cell-contents. In more highly developed plants it will be 

 necessary to take thin sections from different parts, and 

 in different but definite directions. These sections may 

 be made by hand, or between pieces of pith or cork by 

 means of a section-cutter. In some instances some of the 

 methods of staining will also be useful. Dr. Hunt, of 

 Philadelphia, has proposed a plan of staining which is 

 well adapted to all vegetable tissues. He first soaks the 

 part or section in strong alcohol to dissolve the chloro- 

 phyll, then bleaches it in a solution of chlorinated soda. 

 It is then placed in a solution of alum, and afterwards in 

 one of extract of logwood. By transferring it to weak 

 alcohol and afterwards to stronger, it is deprived of its 

 water, and after being made transparent with oil of cloves, 

 it is ready for mounting in balsam or dammar varnish. 

 Care must be taken to wash it well after each of the 

 preliminary steps before staining. 



In the higher algre, the layers of cells assume various 

 sizes and shapes, and the nature of their fructification is 

 of great interest. Sections may be made of the " recep- 

 tacles " at the extremities of the fronds, which contain 

 filaments, whose contents become antherozoids. The pear- 

 shaped sporangia in the receptacles subdivide into clusters 

 of eight cells, called octospores, which are liberated from 

 their envelopes before fertilization. 



The red sea-weeds, or RhodospermecB, afford many beau- 

 tiful forms for the microscope. The " tetraspores " are 

 imbedded in the fronds. 



