SEA WEEDS 381 



Chordaria flagelliformis, the fronds of which are from four to 

 twenty inches long, of uniform thickness throughout, with long, 

 glistening, soft and slimy branches among which the spores are 

 disposed. It may be found in rock pools at almost all levels. 



In the genus Elachista there are some very small and peculiar 

 weeds that are almost sure to be overlooked by inexperienced 

 collectors. They are parasitic, and are composed of two kinds 

 of jointed threads, the inner of which are forked and combined into 

 a tubercle, while the outer are simple and radiate from the tubercle. 

 The spores are attached to the inner threads. The largest species 

 (E. fucicola) is parasitic on Fucus, growing in brush-like tufts about 

 an inch long. Some of the smaller ones are mere star-like tufts 

 of no attractive appearance, and would be disregarded as trouble- 

 some parasites by most young collectors, but all of them are very 

 interesting objects for the microscope. 



The members of the genus Myrionema are similarly liable to 

 be neglected, for they are minute parasites appearing only as 

 decaying spots on larger weeds, but nevertheless form interesting 

 studies for the microscope. Like the last group, they have two 

 sets of jointed fibres, the inner being branched, and spread over 

 the surface of the plant on which it grows, while the outer are 

 simple and stand out at right angles, but all are united into a 

 rounded mass by a gelatinous substance. Perhaps the best known 

 is M. strangulans, which infests Ulva and Enteromorpha, pro- 

 ducing the appearance of small decaying spots. 



In the genus Leathesia we have other unattractive weeds, the 

 jointed and forked threads of which are all united together into 

 tuber-like fronds that are common on rocks and weeds between the 

 tide-marks. There are three or four species, all similar in general 

 appearance, with the spores distributed among the outer threads. 

 These weeds cannot be satisfactorily pressed and dried in the usual 

 way, and should be preserved in formaldehyde or dilute spirit, when 

 they will always be available for microscopic examination. 



The last genus of the Chordariacece is Mesogloia, so called 

 because the central axis of loosely-packed, interlacing threads is 

 covered with gelatinous substance. Around this axis there are 

 radiating, forked threads which are tipped with clubbed and beaded 

 fibres among which the spores are distributed. One species 

 (M. vermicularis), common in most rock pools, is of a wormlike 

 form, of a dirty olive or yellow colour, with soft, elastic fronds 

 growing in tufts from one to two feet long. M. virescens, also 



