BRYOPHYTES— MUSCI 



287 



not be thicker than 3 n. Iron-haematoxyhn is a better stain for the 

 chromatin and blepharoplasts. 



Although sections 20-50 fx in thickness can be cut to show topog- 

 raphy, it is far better to study such stages in the fresh material. When 

 a particularly fine view 

 is secured in this way, a 

 permanent preparation 

 may be made by putting 

 the piece into 10 per 

 cent glycerin without 

 any fixing or staining, 

 and allowing the glyc- 

 erin to concentrate. 

 Then mount in glycerin 



jelly. 



Archegonia. — The 

 younger stages in the 

 development of the ar- 

 chegonium, up to the 

 time of fertilization, 

 present no difficulties in 

 technique. Trim away 

 the leaves which usually 

 cover the cluster of ar- 

 chegonia, fix in the Chi- 

 cago chromo-acetic-os- 

 mic solution, and cut 

 about 5 n thick (Fig. 

 855). 



As soon as the necks 

 of the archegonia begin 

 to turn brown, troubles 

 begin. The hardened 

 necks are like wire and 

 they pry the sections 

 loose from the slide. Besides, the necks, even as early as the fertilization 

 stage, are usually long and curved, so that it is necessary to cut as 

 thick as 15 to 30 M to get the egg, ventral canal cell, and neck canal cells 

 in one section. Use Land's fixative. Haupt's fixative also holds some 



Fig. 85. — Mnium cuspidatum: A, nearly mature anther- 

 idium in the center, with a young archegonium at the right, 

 and at the left a still younger stage which may develop into 

 either an antheridium or an archegonium; B, a nearly ma- 

 ture archegonium with a young archegonium at the right. 

 Fixed in formalin-acetic alcohol (formalin 10 c.c, acetic acid 

 5 c.c, 50 per cent alcohol 100 c.c.) and stained in safranin, 

 gentian violet, orange. X240. 



