182 Methods in Plant Histology 



inches long, and in the end of each tube place the glass part of a 

 pipette. The tub may be elevated by nailing three narrow boards to 

 the sides so as to form a tripod. Place the bottles or cans of material 

 under the pipettes and let sea-water flow into the tub. 



If such chromic acid material is to be used at once for Venetian 

 turpentine mounts, follow the washing in sea-water by J hour's 

 washing in equal parts sea-water and fresh water (not necessarily 

 running water) and then J hour's washing in fresh water. The 

 material is now ready for an aqueous stain or for 10 per cent glycerin. 

 If desirable to keep it for future staining, put it into 5 or 6 per cent 

 formalin in fresh water. 



Material for sections may be treated in the same way, but it is 

 often better to add 2 to 10 c.c. of 1 per cent osmic acid to 100 c.c. 

 of the chromic-acid solution. The 1 per cent osmic acid should be 

 made up in distilled water. 



For habit demonstrations many of the smaller forms can be 

 floated out and dried on paper. EctocarpuSj Desmotrichum, Dictyota, 

 Cutleria, and even small specimens of Laminaria are quite useful 

 when prepared in this way. Take a light pine board, a little larger 

 than the standard herbarium sheet, float it in a tub of water, place 

 on the board the paper upon which the material is to be mounted, 

 arrange the material with a toothpick or the blunt end of a needle, 

 dipping all or a part of the board under water whenever necessary. 

 Cover with a piece of cheese-cloth, add a blotter or two, as in case 

 of flowering plants, and dry under gentle pressure, changing the 

 blotters frequently. The algae have enough mucilage to make them 

 adhere to the paper. Coarse forms, like Fucus, may need to be held 

 down by strips of gummed paper. 



Sphacelaria. The apical cell of Sphacelaria or the nearly related 

 Stypocaulon affords an excellent study of the structure of cytoplasm. 

 Flemming's weaker solution, with the osmic acid even a little weaker 

 than recommended in the formula, is good for the apical cell and the 

 mitotic figures, which are quite conspicuous. For these features 

 it is a good plan to break off the tips so as to have only pieces 6 to 

 12 mm. long, which will lie flat in the paraffin. The tips should be 

 broken off after the material has been brought into xylol. If 



