154 University of California Publications. [botany 



protoplasm in the center of the frond. This exi)ands and is 

 exposed in a dense growth of interwoven hyphfe which, as the 

 perithecium increases in size, seem to fuse more or less to form 

 the pseudoparenchyma wall while the upper and lower walls 

 become pigmented. While the perithecial wall is forming the 

 central mass of protoplasm seems to become constricted into sev- 

 eral lobes, then a space appears, and finally a rounded cavity 

 with a lining of protoplasmic thin-walled cells or closely inter- 

 woven mycelial threads, from which the asci are developed, later. 

 It is during this expansion of the perithecium that the walls of 

 the frond are rounded outwards, and the algal cells are flattened 

 and rearranged. 



The ostiole is rather small, and very probably is developed by 

 a resorption of the perithecial walls in that region, as there is 

 no indication of either the ostiole or canal in the young immature 

 perithecium. The ostiole is surrounded by a dense growth of 

 slender colorless hyph« which extend into the canal and project 

 into the cavity of the perithecium. The asci develop from the 

 entire inner wall of the perithecium, and from the subhymenial 

 layer, and project into the central cavity. They develop succes- 

 sively, so are found in all stages from the tiny hypha-like 

 projections to the mature ascus with the ripe ascospores. The 

 mature asci are long club-shaped stalked bodies 23-40 /^ long 

 by 7-14 /A wide, and contain eight ascospores. The spores are 

 long and narrow with pointed ends, and walls of medium thick- 

 ness. The spores when stained show a broad equatorial band of 

 protoplasm, within which are numerous granules and oil di'ops. 

 The spores have thin walls, are hyaline and measure from 

 8.5-13.5 /A in length and 3-4 /«■ in width. When discharged the 

 spores are inclosed in a mucilaginous covering, which causes 

 them to adhere rather closely together in masses. 



The Prasiola- composite described above was collected by 

 Prof. W. A. Setchell, in the summer of 1899, in two widely 

 separated localities in Alaska. It was found in great abundance, 

 growing on the rocks near the tide line on the coasts of Unalaska 

 and Kadiak Islands. A Prasiola free from the fungus, and 

 undoubtedly the same species as in the composite, was found on 

 the same rocks. 



