Mar. 1898.] BOTANICAL SOCIETY OF EDINBURGH 1 1 1 



one or several superposed ; zoogonidia maturing within the 

 ^oosporangium and not escaping until after germination." — 

 Lcptomitus, Agardh, Syst. Alg. p. 50; Sacc. Syll. vii. 

 p. 265. 



The only exception to this description is that the con- 

 strictions occur very irregularly. 



When the fungus is alive, its highly granular protoplasm 

 is in a state of very active circulation. Spherical or poly- 

 hedral cellulin-grains are found, usually singly, scattered 

 throughout the filaments, but chiefly at the constrictions, 

 and are mostly large enough to fill up the diameter of the 

 filament. 



" The cellulin-grains, discovered by Pringsheim in the 

 hyphffi of various Saprokgniaccw, have sometimes the form 

 of round or polyhedral plates and are sometimes globular, 

 and often show evident stratification. They are not 

 coloured by iodine solutions, and are even insoluble in 

 concentrated caustic potash solution, but soluble in con- 

 centrated sulphuric acid and in a solution of zinc chloride. 

 Nothing is known of their chemical constitution." — 

 (Botanical Microtechnique, by Dr. A. Zimmermann, 

 Engl, transl. by Humphrey, p. 231; tide " Ueber 

 Cellulinkorner, Ber. d. D. botan. Ges. 1883, p. 288,— 

 Pringsheim.") 



To preserve the fungus, and at the same time stain it 

 for microscopic examination, I placed it in a one per cent, 

 solution of osmic acid for twenty-four hours; this darkened 

 the granular protoplasm and the cell walls, and thus 

 improved them for photographic purposes, but the cellulin- 

 grains were only very slightly darkened. The cellulin- 

 grains seem to have a denser external layer and a less 

 dense central portion, for the outer layer has the appearance 

 of a thick cell-wall. 



Although the chemical constitution of these cellulin- 

 grains is unknown, it is probable that they are forms of 

 reserve food material. 



The zoosporangia seem to be developed as terminal 

 shoots. The end of a hypha becomes densely granular 

 and opaque, reaching a length of 200-220/u, and a breadth 

 of 15-20yLt, then a constriction appears just behind the 

 apex, and growth takes place both in front of and behind 



