15 122 Proceedings of the Royal Irish Academy. 



Aseoeyehus foecundus Cotton, comb. nov. (= PhycoeeJis foecunda Stionif. ; 

 A. sphaerophorus Sauv. ; A. islandicus Jons.). 



Phycocelis foecunda has long baffled algologists. The type-specimen shows 

 that it is an Aseoeyelus, and identical with the jilant so well described by 

 Sauvageau as A. sphaerophorus. The number of ascoeysts varies greatly in 

 different specimens; but, as Stromfelt's name suggests, the sporangia are 

 verv numerous. Common on Ehodymenia palmata. 



A. Saccharinae sp. nov} (Plate X, figs. 4-9). A. affink Cotton, '07, non Sved. 



Plants forming dark brown circular spots 1-2 mm. diam., rarely 3-4 mm. 

 Discoid thallus monostromatic or partly diplostromatic, 8-14 fi thick, not 

 parenchymatous in centre ; margin rather irregular ; radiating filaments 

 regular, 7-8 n wide, by 1-2 times as long; ehromatophores 4-6. Hairs 

 numerous, basal ; sheath well developed ; adult cells 60-80 x 7-8//. 

 Assimilating filaments few or absent, simple, cylindrical, 70-120 /u long, thin- 

 walled ; cells, 7-9 fi wide by 1-2 times as long. Ascoeysts usually abundant, 

 appearing very early on conspicuous wide margin of basal thallus, sessile, 

 rarely stalked, thick-walled towards the base, typically clavate, 30-40 x 9-10 u 

 'on young plant sometimes globose, 15 x 20 x 10-14 /j). Unilocular sporangia 

 unknown. Plurilocular sporangia very abundant, sessile, subsessile, or stalked, 

 lanceolate or elliptic-oblong, rather small, 30-40 x 10 fi (on old plants 

 30-55 x 10-12 fi), 1-2 seriate; locali 4-6 p. high. 



Habitat. — On Lamina ria saccharina. 



Fruiting Season. — Early spring till late autumn. 



Distribution. — England (Swanage, "vTeymouth, Plymouth), Ireland (Clare 

 Island). 



This species, hitherto undescribed, is not uncommon on the south coast of 

 England, and was found more than once on Clare Island. It occurs on young 

 plants of L. saccharina, usually on the decaying tips of the fronds, where it 

 forms dark-brown spots often intermixed with Myrionema Corunnae. It may, 

 however, also occur on older fronds, in which case it is usually larger and 

 often presents irregularities in microscopic structure. 



The species most closely resembles A. foecundus, but it differs in the 

 typically clavate ascoeysts, although in young plants there is a tendency for 

 these bodies to be subglobose. The spots formed are not so large, and the 



1 Maculae minutae, fuscae 1-2 (raro —4) mm. diam. Discus unistratosus vel partim duostratosus, 

 cellulis circa 12—16 x 6—8^, organa verticalia emittens (1) pilos numerosos, cellulis 60 x 80 x 7-8 in, 

 (2) fila assimilantia rara, brera, 7-9 /» lata, chromatophoris 4-6, minutis (3) sporangia plurilocularia 

 numerosissima, sessiiia vel breviter aut interdum longius pedicellate, elliptico-oblongata, 1-2 seriata, 

 plerumque 30-40 x 10 n- 



