80 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



rructification borne at the base of cortical filaments ; i)lurilocular spo- 

 rangia cylindrical, composed of few cells in a row j unilocnlar sporan- 

 gia globose. 



Fronds forming small tufts on other algse. 



Cortex with a series of exserted colored filaments Elacliistea, 



Cortex destitute of exserted filaments Myriactis. 



Fronds irregularly globose, hollow at maturity Leathesia, 



ELACHISTEA, Duby. 



(From £/MxtGTa, very small.) 



Fronds olive-brown, tufted or pulvinate, basal portion solid, some- 

 what parenchymatous, composed of densely packed branching fila- 

 ments, which become free at the surface and branch corymbosely so as 

 to form a layer of short filaments (paraphyses), at the base of which are 

 borne the sporangia of both kinds and a series of long exserted fila- 

 ments ; hairs formed at the base of the paraphyses, exserted ; uniloc- 

 ular sporangia rhombic-ovoid, plurilocular sporangia cylindrical, com- 

 posed of a few cells in a linear series. 



A genus consisting of a few sjiecies, all of which form small tufts on other alga?, 

 esi^ecially on Fucacecc. They may be recognized by the double series of filaments 

 borne on the surface of the solid and but slightly developed basal portion. The 

 longer filaments and hairs float freely in the water, but the shorter paraphyses are 

 I)acked rather closely together, forming as it were a definite cortical layer over the. 

 basal portion. The unilocular sporangia are common. The more or less solid basal 

 portion of the fronds in some of the species gives off filaments which penetrate, 

 into the substance of the algJB on which they are growing, and by the growth and 

 persistence of these filaments it may be that the species are propagated from year to 

 year, as happens in the case of certain fungi. In other species no penetrating basal 

 filaments have as yet been found. 



The limits of the si^ecies are pretty well defined except in the case of ^. fucicola, E. 

 hihrica, and E. flaccida, where it must be confessed the species show a tendency to run 

 into one another. In the present case we have included in Elacliistea only the species 

 in which, besides the paraphyses which cover the surface, there are .long projecting 

 colored filaments as in E. scutulata, on which Duby founded his genus Elacliistea in the 

 Botanicon Gallicon. Here undoubtedly belong E. fucicola and its allies, but the same 

 can hardly be said of ^. pulvinata, which was made by Kiitzing the type of his genus 

 Mijnactis. In this species the surface of the frond is covered by the paraphyses, but 

 there is not in addition a series of elongated filaments asin E. fucicola, for the exserted 

 hairs in E. pulvinata are of a quite difierent nature. We have referred E. pulvinata to 

 the genus Myriactis, not, however, limiting the genus as Kiitzing has done, for some of 

 the forms placed by him in Plujcopliila should be referred to Myriactis, although the 

 greater part of them are correctly placed by algologists in Elacliistea. It may be that 

 there exist forms intermediate between the true ElacMsiece. and Myriactis, but, from the 

 study of dried specimens, we have not been able to come to such a conclusion. It 

 should be remarked that M. pulvinata is placed in Elachistea by the most prominent 

 algologists, as Thuret and Bornet, Agardh, Harvey, Le Jolis, and others. The uni- 

 locular sporangia are most common in summer, and the plurilocular sporangia are more 

 frequent early in the season. 



