BRYOPHYTES— HEPATICAE 



277 



are borne upon stalked receptacles, it is better to make separate 

 preparations to show the structure of the mature thallus. Sections 

 intended to show the 

 structure of the mature 

 thallus should be 15 to 

 25 II in thickness, but 

 sections to show the 

 growing point and de- 

 velopment of the thallus 

 should not be thicker 

 than 10 fx. The apical 

 region of the Junger- 

 manniaceae (Figs. 77, 

 78) affords an excellent 

 opportunity for studying the development of the plant body from a 

 single apical cell. 



B 



Fig. 77. — Plilidiam ciliare: A, longitudinal section, and 

 B, transverse section of the apical region of the leafy game- 

 tophyte. Fixed in chromo-acetic acid and stained in Dela- 

 field's haematoxylin. X420. 



Fig. 78. — Pellia epiphylla: photomicrograph of apex of gametophyte showing apical cell and 

 segments; fixed in chromo-acetic-osmic acid and stained in .safranin, gentian violet, orange The 

 negative was made by Dr. Kohler at the Zeiss factory in Jena, Germany. 



Safranin, gentian violet, orange, is good for forms like Pellia, where 

 even the apical cell is vacuolated, since it not only brings out the cell 

 walls but stains the plastids and other cell contents (Fig. 78). The 

 chloroplasts and leucoplasts are well differentiated by this stain. 



