— 150 — 



about I— 2mm. in diameter on llie surface of the Rhodymenia. Tliese 

 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 

 ascocystse. 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/i 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 1 pt 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// long and 9 — 12// broad, they are somewhat clavate, or 



Fig. 12. Ascocyclns islandicua. Fragments of radial fitaments. 

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

 the left; b, 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 (x 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 



