80 REPORT OP COMMISSIONER OF FISH AND FISHERIES. 



Fructification borne at the base of cortical filaments ; plurilocular spo- 

 rangia cylindrical, composed of few cells in a row ; unilocular sporan- 

 gia globose. 



Fronds forming small tufts on other alga3. 



Cortex with a series of exserted colored filaments ElacMstea. 



Cortex destitute of exserted filaments Myriactis. 



Fronds irregularly globose, hollow at maturity Leathesia. 



ELACHISTEA, Duby. 



(From elaxioTa, 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 species, all of which form small tufts on other algse, 

 especially on Fucacew. 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 

 packed 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 algae 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 species are pretty well defined except in the case of E. fucicola, E. 

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

 into one another. In the present case wo have included in ElacMstea 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 ElacMstea in the 

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

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

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

 there isnot in addition aseries of elongated filaments as in E. fucicola, for the exserted 

 hairs in E. pulvinata are of a quite different 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 PhycopMla should be referred to Myriactis, although the 

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

 there exist forms intermediate between the true ElacMsiem 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 ElacMstea 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. 



