Bryophytes Hepaticae 



211 



of osmic acid for 2 or 3 minutes, allow the drop to dry up, pass the 

 slide through the flame two or three times, as in mounting bacteria, 

 and then stain sharply in acid fuchsin. This should show the general 

 form of the antherozoid, and will usually bring out the cilia. 



The Archegonia. The methods for archegonia are practically the 

 same as for antheridia. Too much stress cannot be laid upon the 

 importance of carefully 

 selecting the material. 

 Use very small pieces, 

 and, before placing them 

 in the fixing agent, trim 

 them to such a shape 

 that the position of 

 the archegonia will be 

 known accurately even 

 after the pieces are im- 

 bedded in paraffin. 



For stages like those 

 shown in Fig. 63, A and 

 B, safranin with anilin 

 blue or light green is a 

 good stain and 7 to 10 ju 

 is about the right thick- 

 ness. 



For stages like C, in 

 such forms as Mar- 



chantia, where the necks are long and often somewhat curved, it is 

 better for general purposes to use sections about 15 ju in thickness. 

 If it is desired to obtain preparations showing the cutting off of the 

 ventral canal cell, the development of the oosphere, and the process of 

 fertilization, the sections should be from 3 to 6 ju. in thickness. 



For archegonia containing young embryos, like that shown in D, 

 Delafield's haematoxylin without any counter-stain gives beautiful 

 preparations when the staining is well done. It is easier for the 

 beginner to get good preparations with the safranin, gentian-violet, 

 orange combination. ' 



FIG. 63. Marchantia polymorpha: A, three early 

 stages in the development of archegonia Delafield's 

 haematoxylin; B, young archegonium showing two 

 neck canal cells and the central cell before the cutting off 

 of the ventral canal cell fuchsin and methyl green; C, 

 mature archegonium immediately before the fertiliza- 

 tion period safranin, gentian- violet, orange; D, young 

 embryo Delafield's haematoxylin. X400. 



