275 



stratum, mostly about 800 p. 

 long; the cylindrical part is 

 about 40 IJL thick. 



The creeping filaments 

 have thick walls and sinu- 

 ated periphery, the filaments 

 being thickest at the cross- 

 walls; the filaments are 

 about 100 150 // or thicker. 

 The length of the pericen- 

 tral cells in these filaments 

 varies about 150 //. 



From these creeping 

 filaments the erect ones 

 grow up. The peripheral 

 walls in these are still thick 

 at the base but upwards 

 they soon become thin. The 



Fig. 274. Polysiphonia ma- 

 crocarpa Harv. a, summit of 

 a filament with young cy- 

 stocarps. b, transverse sec- 

 tion of a filament, (a, about 

 200:1, b, 150:1). 



Fig. 273. Polysiphonia macrocarpa Harv. 

 Part of a female plant. (About 16:1). 



filaments are about 100^ thick, but both 

 thinner and thicker ones are to be found. 

 The length of the cells in these filaments 

 is rather variable. Generally they are 

 about one and a half to twice as long 

 as they are broad, but often they are 

 three to four times as long or even 

 longer. Upwards the filaments taper 

 gradually and in the upper ends they 

 are only 20 25 // thick. 



The erect filaments are often un- 

 branched at their base. If we examine 

 such a young filament in vigorous growth 



18* 



