﻿230 BOTANICAL GAZETTE [march 



very large amount of the fungus. The algal cells are distributed singly or in 

 groups, contained in capsules formed by a network of hyphae and in a gela- 

 tinous matrix. There is a central zone of mycelium so thick that the two 

 layers of algal cells are widely separated. The perithecia are blackish swell- 

 ings on the surface of the thallus, the cavity is lined with a pseudoparenchy- 

 matous layer from which the asci arise and there is a well-developed ostiole, 

 lined with hairs that project outward. The ascospores are discharged in great 

 numbers and germinate readily. It is probable that the germ tubes enter the 

 Ulva sporeling at very early stages of development, and that they do not attack 

 mature plants, for the latter have never been found partially infected. So 

 the alga and fungus seem to develop together almost from the germination 

 of the respective spores. 



The Prasiola-composite came from Alaska. The fungus Gidgnardia 

 alaskana n. sp. changes the character of the Prasiola plant (which is a new 

 species, named Prasiola borealis), coloring it darker, and giving it a curled 

 crinkled, and leathery texture in old plants. The monostromatic fronds 

 become from 8-16 layers of cells thick after infection, and the algal cells are 

 scattered very irregularly in the mass of mycelium. Another Prasiola-com- 

 posite has been known for some years from the Antarctic, first described by 

 Hooker (1845) under the name of Mastodia tessellata, its true nature being 

 discovered by Hariot in 1882. The relation of the fungus to its algal host 

 in these three composites is apparently essentially the same as in the lichens. 

 The fungus must depend upon the alga for its organic material, and conse- 

 quently operates as a parasite. Whether the alga gets any benefit from the 

 association is very problematical. It is possible that the tougher texture of 

 the frond may better resist wind and wave, but marine algae are generally 

 well able to care for themselves in these respects and non-infected material 

 grows successfully side by side with the composite plants. 



It seems plain that these composite organisms are lichens, certainly as 

 much so as is Ephebe, and we wonder if the author has special reasons for 

 avoiding that name, and whether she thinks it should be replaced by a term 

 indicating the dual nature of these plants. — B. M. Davis. 



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