74 Methods in Plant Histology 



A square or round hole f inch in diameter is cut in a piece of 

 pasteboard f inch thick, 1 inch wide, and 1J inches long. The paste- 

 board is then boiled to sterilize it and to make it fit more closely to 

 the slide. While the pasteboard is still wet, press it to the slide, 

 make the culture in a drop of water or culture solution on the cover, 

 and invert the cover over the hole. A little water added at the edge 

 of the pasteboard from time to time will keep it from warping and 

 will at the same time provide a constant moist chamber. 



In collecting material for mitotic figures in anthers it is neces- 

 sary to examine fresh anthers, if one wishes to avoid a tedious and 

 uncertain search after the anthers have been imbedded. By teasing 

 out a few cells from the apex and a few from the base of the anther 

 the stage of development is readily determined, and anthers which 

 do not show the desired stages can be rejected. By allowing a drop 

 of eosin or methyl green to run under the cover the figures are more 

 easily detected. The actual progress of mitosis has been observed 

 in living stamen hairs of Tradescantia. 



MICROCHEMICAL TESTS 



During the past ten years there has been such an advance in 

 botanical microchemistry that whole books are devoted to the 



\j 



subject, and it would be impossible to give any complete presentation 

 in a book intended for students of morphology. Pflanzenmikro- 

 chemie, by Dr. O. Tunmann (Gebriider Borntraeger, Berlin), is 

 recommended to those who read German. Zimmerman's Botanical 

 Microtechnique (Henry Holt & Co., New York) is still recommended 

 to those who must rely upon English. We shall give only a few 

 tests, but in considering the various stains we shall indicate the 

 effect of each stain upon the various plant structures. 



Starch. Mount the starch or starch-containing structures in 

 water, and allow a drop of iodine solution to run under the cover. 

 Starch assumes a characteristic blue color. The solution may be 

 prepared by dissolving 1 g. of potassium iodide in 100 c.c. of water 

 and adding . 3 g. of sublimed iodine. A strong solution of iodine in 

 alcohol (about 1 g. in 50 c.c. of absolute alcohol) keeps well. A drop 

 of this solution added to 1 c.c. of water is good for testing. With too 

 strong a solution, the starch first turns blue but rapidly becomes black. 



