Holtz: OBSERVATIONS ON PELVETIA. 4] 
Methods: fixing and mounting fluids. — Material fixed and 
preserved in formalin was employed. ‘This was washed in 30 
per cent. alcohol, as fresh water alone caused injurious swelling 
of the laminze. The material was then passed into higher per 
cents of alcohol to harden and dehydrate. ‘The complete de- 
hydrating seems to cause tensions in the body of the plant result- 
ing in tearing apart of pith cells, the intercellular jelly giving 
way. But occasional very perfect pith sections may be thus 
obtained nevertheless, and by comparing with sections cut from 
70 per cent. or 80 per cent. alcoholic material and mounted in 
water or glycerine the nearly natural appearance of these cells 
can be observed. 
Most of the drawings were made from dehydrated material, 
and must therefore be somewhat unnaturally contracted. Where 
water or glycerine mounts were made and drawings from them, 
it is so indicated in the notes explanatory of the plates. The 
gelatinous walls swell greatly in glycerine (as compared with 
alcohol) but as the cross-sections of the lamina and stipe, for 
instance, have practically the same dimensions as the formalin 
material it may be assumed that the glycerine mounts give a 
truer picture of the tissues than do the balsam mounts. 
Sectioning. — Most of the sections, especially the serial 
sections illustrating conceptacle development and the growing 
point, were made with a microtome from material imbedded in 
paraffine. After the work of hardening is once started this 
method is probably as rapid as any where imbedding is neces- 
sary. Some sectioning was done with a hand microtome, the 
75 per cent. or 85 per cent. material being held in a pith clamp. 
Such sections were mounted generally in glycerine. These 
sections however showed a tendency to curl more than paraffine 
sections. | 
Statning.— A variety of stains were tried. Many of the 
ordinary wall stains proved entirely ineffectual. At length the 
following stains were selected as the best. 
Fuchsine and methyl violet is perhaps the most generally 
useful. This mixture stains quickly and deeply. Washing 
cautiously in acid alcohol brings out different effects. Only 
a little washing leaves the gelatinous matrix slightly stained, the 
inner walls stain deeply, while the cell contents again take a 
slight coloring. Differentiation is brought out nicely, generally 
by more washing, in the conceptacular parts. The granular 
