98 METHODS IN PLANT HISTOLOGY 



xylol and the transfer from xylol to balsam. The process is tedious, 

 but the mounts are very firm and durable. The Venetian turpentine 

 method is less tedious and is likely to produce better results than the 

 method just described. Fix in the chromo-acetic mixture just men- 

 tioned. Stain some prothallia in iron-alum haematoxylin and some in 

 phloxine and anilin blue. When both have reached the thick turpen- 

 tine, fine preparations can be made by mounting prothallia from both 

 lots under the same cover. 



Sori of ferns. — Instructive mounts of sori or of individual sporan- 

 gia may be made without sectioning. It is better to choose ferns with 

 thin leaves, since leaves thicker than those of As-plenium thelypteroides 

 are likely to be unsatisfactory. If this fern is at hand, cut off several 

 of the small lobes which bear from three to six pairs of sori. Fix in 

 chromo-acetic acid; wash in water; stain in Delafield's haematoxyhn, 

 or omit staining altogether; pass through a series of alcohols, allowing 

 each grade to act for at least 10 minutes; clear in clove oil; and mount 

 in balsam. If the sori have begun to turn brown, better views of the 

 annulus will be obtained without staining. 



Mosses and liverworts. — Nearly all mounts are more successful by 

 other methods, for which the student should consult the chapters on 

 Bryophytes (chaps, xxi and xxii). Excellent mounts of the peristome 

 of the moss can be made as follows : From fresh or preserved capsules 

 cut ofif the peristome just below the annulus. Treat with 95 per cent 

 alcohol 10 minutes, absolute alcohol 10 mmutes, clear in clove oil or 

 xylol, and mount in balsam. It is a good plan to put at least three 

 peristomes on a slide, one with the outside up, one with the inside up, 

 and another dissected to show details of the teeth. 



Fairly good unstained mounts of the archegonia and antheridia of 

 small mosses can be obtained by following the directions for mounting 

 the sori of ferns. 



Beautiful and instructive mounts of the more delicate foliose 

 Jungermanniaceae can be made by staining lightly in Delafield's hae- 

 matoxylin whole plants, or pieces as long as can be covered conven- 

 iently. The method is that just given for fern prothallia. The mount 

 should show both dorsal and ventral views. 



The epidermis shows its best surface views without sectioning. Se- 

 lect some form with large stomata, hke Lilium or Tulipa, strip pieces 

 of epidermis from both sides of the leaf, and place them immediately 

 in absolute alcohol for 10 minutes. Stain in Delafield's haematoxylin; 



