200 BIOLOGICAL LECTURES. 



apple (Fig. 5) as an illustration of the former group ; while 

 entire and sectioned seeds, as well as the contained embryo of 

 seeds like the bean, ash, maple, oak, beech, etc., can often be 

 serially displayed to advantage. 



A good many objects, especially cryptogamic ones, should 

 be displayed in mass as well as singly. As a case in point we 

 might cite a tuft of fern prothallia that has grown on a tena- 

 cious soil, and which may probably show all stages of maturation 

 in the oophyte and seedling sporophyte. Such a tuft would 

 inevitably fall to pieces if placed in alcohol directly when gath- 

 ered ; but if imbedded in a black-pigmented matrix of plaster 

 of Paris, the prothallia when bleached stand out in fine relief. 

 Antheridial and archegonial tufts of various mosses and of 

 Marchantia can be similarly treated. 



(d) Finishing of preparations. When a green plant is placed 

 in alcohol and exposed, as already recommended, to bright sun- 

 light, the discharge of color is rapid, but the specimen should 

 be exposed for several days. Where plants contain tannin 

 compounds, however, a few drops of dilute hydrochloric acid 

 should be added to the alcohol, otherwise the object will assume 

 a dirty brown color. When the specimen is decolorized, the dis- 

 colored liquid should be carefully poured out, or drawn off by 

 a siphon, as the object has been made extremely brittle. Pure 

 distilled alcohol should then be added, and the preparation put 

 aside on a rather large table along with others that are ready 

 to be sealed up. After the waste alcohol has accumulated for 

 a time it can be passed through a still, and a clear, sparkling 

 liquid is then obtained that is even superior to new alcohol. 



Probably no step in the process of preservation requires 

 more attention than the sealing of the jars. It is a truly diffi- 

 cult matter to obtain a cement which will resist alcohol. Six 

 years of trial incline me to recommend the following : Four 

 parts of plaster of Paris, one part of glue, and one-fortieth part of 

 red lead, intimately mixed together when the glue is melted and 

 hot. Previous to its application the cork of the bottle should 

 have been pressed home till its upper surface is one-sixteenth 

 inch below the top of the neck, and its lower surface slightly 

 above the alcohol. At this time care should be taken not to 



