— 150 — 



about 1— 2 mm. in diameter on the surface of the Rhodymenia. These 

 spots are of a brown colour in material, which has been conserved 

 several years in alcohol , owing to the colour of the contents of the 

 ascocystæ. The basal portion of the frond is a more or less orbicular 

 disc with marginal growth ; the margin is either entire or sometimes 

 consisting of free, creeping filaments. The disc is for the most part 

 monostromatic and only here and there diplostromatic, it is 6 — 12// thick. 

 The length of the cells is about 7 — 14//, the marginal cells being often 

 somewhat longer. It is not difficile to remove the disc from the sub- 

 stratum with a razor, and the radial filaments are easily separable. 



The erect portion of the frond consists of hairs, ascocysts, assimilative 

 filaments and plurilocular sporangia. The hairs are abundant and spring- 

 all from the basal disc, they are 7 // thick and attain a length of 400 

 — 500//, their basal cell is usually long, and the growing point is situated 

 above it. The base of the hairs is inclosed in a sheath. The ascocysts 

 are 23 — 29 f± long and 9 — 12 // broad, they are somewhat clavate, or 



f e 



Fig. 12. Ascocyclus islandicus. Fragments of radial filaments. 

 a showing an assimilative filament to the right and a sessile sporangium to 

 the left; 6, c, d show stalked plurilocular sporangia. The length of the stalk 

 increases towards the centre ; a belongs to a portion near the margin, d is 

 nearest the centre, e, f fragments of radial filaments near the margin showing 

 young erect filaments, ascocysts and sessile plurilocular sporangia. (316 : 1.) 



sometimes thickest in the middle and almost elliptic. They occur here 

 and there over the whole disc scattered between the sporangia or the 

 young filaments. They are filled with yellow-brown contents. 



The assimilative filaments are unbranched, 80 — 150 p long and 

 7 — 10/!/ broad, they are scattered between the sporangia; their cells are 

 somewhat longer than they are broad, but sometimes the apical cell is 

 thrice as long as broad. The plurilocular sporangia are 29—50 // long 



