Clearing and Staining of Leaves and Stems. 93 



soil-water, but in some cases quite as clearly with temperature. 

 Other factors, especially aeration and percentage of alkali salts, 

 apjiarently have a dominant influence in one or more of these 

 associations. 



NOTES UPON THE CLEARING AND STAINING OF 



LEAVES AND vSTEMS. 

 By L. M. Peace. 



Leaves and stems of the higher plants, which have been 

 dried, or kept in formaldehyde or some other of the usual pre- 

 servatives, often have been bleached and cleared with the 

 greatest difficulty, when they were wanted for histological stud- 

 ies. It was found that the materials varied in their susceptibil- 

 itv to the different methods of clearing. In general, the worker 

 had to try all of the known methods in order to find the one which 

 would satisfactorily bleach and clear his material. If he were 

 studying some plants, such as those of the desert, which plants 

 usuallv contain much coloring matter, he may not have found 

 anv method altogether satisfactory. 



Of the methods in general use, only Eau de Javelle will 

 clear some of these plants, but the employment of this reagent 

 is undesirable, since it may destroy the tracheal elements of the 

 tender leaves and young stems. When examined with the micro- 

 scope, small leaves, which have been cleared in Eau de Javelle, 

 often show no traces of the tracheal elements of the veins. 



After considerable experience with the various well known 

 bleaching and clearing reagents, it has been found that all kinds 

 and conditions of available leaves and stems, or sections of leaves 

 and stems as the case may be, are readily and satisfactorily 

 bleached and cleared by the following method: 



Place whole leaves, if they are small, or parts of them if 

 they are large, and sections of stems as the case may be, for from 

 one to three davs or a week, in a saturated aqueous solution of 

 chloral hydrate ; rinse thoroughly in water, and place for a simi- 

 lar length of time in a five per cent solution of potasium hydrate. 

 The specimens should now be thoroughly bleached and cleared 

 of all cell contents. They may now be transferred to seventy 

 per cent alcohol, dilute glycerine, or to a saturated aqueous 



