Pteridophytes Filicales 235 



terial is easily cut in paraffin. Older portions should be cut freehand. 

 Osmunda affords an excellent illustration of the mesarch siphonostele. 



For illustrating the amphiphloic siphonostele, or solenostele, 

 the rhizome of Adiantum, the maiden-hair fern, will furnish material. 

 No better material could be found for illustrating the leaf gap and 

 leaf trace. 



The ferns of the Gray's Manual range afford no very satisfactory 

 material for illustrating the protostele, although protosteles occur 

 in Lygodium and Trichomanes. The most satisfactory material is 

 Gleichenia, a very common and very beautiful fern in tropical and 

 subtropical regions, but almost never seen in greenhouses nor even in 

 botanical gardens. Formalin alcohol material is easily cut without 

 imbedding and is easy to stain. 



The stems of tree ferns require special treatment. With the 

 large leaf bases partly cut away with a sharp razor, transverse sec- 

 tions are easily cut for a considerable distance below the apex. 

 Material fixed in formalin alcohol cuts very well. If fresh material 

 is to be cut, the softer portions should be flooded with alcohol after 

 each section. Farther down, there will be a region where sections 

 can be cut without any flooding, and still farther down, it will be 

 difficult or impossible to cut sections across the whole stem. Sec- 

 tions 1 or 2 cm. thick, cut smooth on the ends, may be kept in 95 per 

 cent alcohol or in glycerin in large glass dishes of the Petri dish 

 pattern. 



Roots are easy to secure and easy to prepare. For mitotic figures 

 and the development of the root from the apical cell, fix the tip in 

 chromo-acetic acid with a little osmic acid. If the development of 

 the root is the principal object, stain in safranin and light green, or 

 in the safranin, gentian-violet, orange combination; if mitotic 

 figures are to be studied, stain in iron-haematoxylin with a very 

 light counter-stain in orange. 



Roots of tree ferns are sometimes available in greenhouses. In 

 some species the stem is covered by a dense felt of small roots, some 

 of which will be white and soft at the tip. These roots are likely to 

 have about the diameter of onion root-tips, and the beauty of prepara- 

 tions made from them could hardly be excelled. In the tropics, where 



