636 



Journal of Applied Microscopy. 



Fig. 3. Marchantia polymorpha. X 400. 

 Three early stages in the development of the archegonia. 



Dela- 



field's hjEmatoxylin. 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 

 just ready for fertilization. Safranin-gentian violet-orange. D. 

 Young embi-yo. Delafield's hjematoxylin. 



with or without a faint trace of erythrosin or orange G, or use a mixture of acid 



fuchsin and methyl green. Nothing but practice and patience will bring success 



in such critical work. 



If antherozoids are found 



escaping, transfer them to a 



small drop of water on a clean 



slide, invert the drop over a 



one per cent, solution of osmic 



acid for two or three 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 meth- 

 ods for archegonia are practi- 

 cally 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 accurately known even 



after the pieces are imbedded in paraffin. For stages like A and B, Delafield's 



hsematoxylin is a good stain, and 10 /i is about the right thickness. For stages 



like C, in such forms as Marchantia, where 

 the necks are long and often somewhat curved, 

 it is better for general purposes to use sections 

 from 15 /< to 20 yu in thickness. If it is de- 

 sired to obtain preparations showing the cut- 

 ting off of the ventral canal cell, the develop- 

 ment of the oosphere and the process of 

 fertilization, the sections should be from 5 }x 

 to 10 /^ in thickness and the same staining 

 may be used as for the development of 

 antherozoids. For archegonia containing 

 young embryos, like that shown in D, Dela- 

 field's hsematoxylin without any counter stain 

 is to be recommended. 



The sporophyte. — Sporophytes in early stages 

 of development often yield good preparations 

 without very much trouble, but in later stages 

 they are frequently difficult to cut on account of 

 the secondary thickening of the capsule wall, 



Fig. 4. Ricciocarpus natans. X 104. 

 Young sporophyte enclosed in the archego- 

 nium. Spore-mother-cell stage. All 

 the cells of the sporophyte except a 

 single peripheral layer (dotted in the 

 figure) produce spores. Fixed in picro- 

 acetic acid and stained in Delafield's 

 hematoxylin. Celloidin section 30 

 microns in thickness. 



