II2 
plants referred to by Cotton in the Clare Island Survey, 
p. 120, which he suggests, may easily be mistaken for 
Sphacelaria vadicans. In the Isle of Man district Sphac- 
elaria cirrhosa var. fusca rarely occurs with sporangia. 
Occasional unilocular sporangia have been found in the 
winter but the plant relies chiefly on the production of 
propagules as a means of spreading. The plants described 
under the name of var. fusca agree with the illustration 
given in Harvey’s ‘‘ Phycologia Britannica,’ Vol. I, 
plate 149, except for the propagules. In Harvey’s figure 
the propagules shew attenuated apices usually regarded as 
characteristic of branches of limited growth whereas the 
ends of the radiating branches of the propagules on the 
Manx plants shew enlarged apices usually associated with 
branches of unlimited growth. 
8. Sphacelaria bipinnata, Sauv. 
_ This plant is very similar in habit and general appearance 
to Sphacelaria cirrhosa var. pennata Hauck but it is almost 
restricted to the thalli of Halidrys siliquosa. It forms 
conspicuous globular masses when mature and was there- 
fore originally called Sphacelaria cirrhosa var. egagropila 
by Griffiths. The globular habit is not the result of rolling 
and tangling of the branches, but is due to regular radia- 
tion of the main fronds, hence the name aegagropila is 
undeserved and has been corrected by Sauvageau to 
Sphacelaria bipinnata. The true aegagropila or rolled 
form of Sphacelaria cirrhosa has not been found in this 
area. 
g. Ascocyclus. 
Ascocysts distinguish the genus Ascocyclus from other 
genera such as Myrionema or small Ectocarpi with which 
it is readily confused by the beginner. Ascocysts are 
spherical, ovoid, elongate or cylindrical cells filled with 
a dark brown homogeneous material whose composition 
and function is somewhat uncertain. See Figure 26. 
