Journal of Applied Microscopy. 



635 



JouflflPP.Mic. 



Fig. I. Ptilidium ciliare. X 420. 

 A, longitudinal ; B, transverse section of the apex of the leafy 

 gametophyte. Fixed in Flemming's weaker solution, stained 

 in a mixture of acid fuchsin and iodine green. Ten microns. 



is easily gotten into paraffin even in forms like Ricciocarpus, which in their 

 mature condition are in danger of collapsing. The apical region of the foliose 

 Jungerrrranniaceffi afford an excellent opportunity for studying the development 



of the plant body from a single 

 apical cell. If mixtures con- 

 taining osmic acid are used for 

 fixing, there may be difficulty in 

 the staining even after using 

 peroxide of hydrogen. Cor- 

 rosive sublimate-acetic, Carnoy's 

 fluid, or chromo-acetic acid are 

 better for apical regions. A 

 fairly vigorous staining with a 

 mixture of acid fuchsin and 

 iodine green often brings the 

 walls out very sharply. Chromo-acetic acid followed by Delafield's haematoxylin 

 or Bismark brown is good for apical cells and developing regions, but a light 

 counter stain with erythrosin improves preparations of the mature thallus. After 

 corrosive sublimate-acetic the material may be stained in bulk with alum 

 cochineal or alum carmine, thus giving fairly good preparations and saving 

 considerable labor. 



Antheridia. — If you have the material it is not difficult to get good prepara- 

 tions showing the development of antheridia. In forms like Asterella, Fellia, 

 etc., cut out a small portion of the thallus bearing the antheridia. The piece 

 should not be more than a quarter of an inch square, and if it can be smaller, so 

 much the better. For early stages of the antheridia of Marchajitia, select young 

 antheridiophores which still lie close to the thallus. These readily cut as thin 

 as 5//, and a single slide will usually show a more complete series than is repre- 

 sented in the figure of Asterella, 

 but after the stalk begins to 

 lengthen the younger stages 

 become infrequent and it is not 

 always easy to cut thin sections. 

 Delafield's haematoxylin or Bis- 

 mark brown serves very well for 

 such stages as are shown in the 

 figure. The protoplasm of the 

 young antheridia is so dense 

 that the addition of a counter 

 stain is almost sure to injure 

 the preparation by obscuring 

 the cell walls. For stages older 

 than that represented in D, showing the development of the spermatozoid, the 

 paraffin must be rather hard (melting at 55°C to 65°C), and the sections should 

 not be thicker than 5 }a, while 2 /.< or 3 /.< is best. For such stages use the 

 safranin-gentian violet-orange combination, Heidenhain's iron alum haematoxylin 



Jour /jpp AJic. 



Fig. 2. Asterella hemisphjerica. X 255. 

 Successive stages in the development of antheridia. Fixed in 

 chromo-acetic, stained with Delafield's hsmatoxj'lin. Section 

 ten microns thick. 



