246 
Pon l ton. — The Structure and Life-history of 
2. Pyreimla margacea , Ach. L. Univ. p. 315, T. V. f. 3, 1810. 
3. Verrucaria margacea, Wahl. FI. Lapp. p. 465, 1812. 
4. Pyrenula margacea , Ach. Syn. Meth. Lich. p. 127, 1814. 
5. Verrucaria margacea, Wahl. FI. Suec. p. 872, 1826. 
6 . Verrucaria submersa , Borr., E. Bot. Suppl. No. 2768, 1834. 
7. Verrucaria margacea , Leighton, Ang. Lich. p. 62, Plate XXVI, 
1851. 
8. Verrucaria margacea , Leighton, Lich. FI. p. 446, 1879. 
Acharius has considered the first four as synonymous, Wahlenberg the 
first five. Leighton regards all the above as synonymous, Borrer the 
first six. 
Acharius 1 includes V. papillosa among his synonyms, but the synonymy 
of V. margacea and V ’. papillosa is doubtful. The thallus of V. margacea 
does not closely agree with that described for V. papillosa , neither are the 
perithecia of V. margacea ‘ semi-immersed in thalline elevations’. Leighton 2 
describes V. papillosa as a distinct species. His figure does not agree with 
V. margacea. On the whole it seems more natural to place V. papillosa as 
a variety of V. margacea as Leighton does later. 3 
Borrer 4 gives a description of V. submersa , also figures, which closely 
agree with V. margacea. He thinks, however, that V. submersa may be 
identical with V. mucosa as described by Wahlenberg 5 and Acharius. 6 It 
is, however, obvious from the descriptions of V. mucosa that it is quite 
a distinct species. Borrer also suggests a resemblance to V. nitida , which 
is equally distinct both in structure and habitat. 
Mudd 7 recognizes two totally distinct organisms on the ground of 
difference in spores. He says (1. c., p. 286) ‘ I cannot see how Leighton 
reconciles the fig. of the spores of V. submersa in E. Bot. Suppl. 2768 with 
those of his V. margacea. In E. Bot. they are represented as elliptical, 
unilocular, sub-hyaline ; in his Brit. Ang. Lichens, as linear quadrilocular, 
and coloured ’. Mudd then distinguishes V. submersa , Borr. ( V. chlorotica , 
Ach. Syn. 94 in pt.) (1. c. p. 286), and Thelidium cataractum , Hepp. (1. c. 
p. 294), to which he refers V. margacea of Leighton. 8 The genus Verru- 
caria is regarded by Mudd as possessing colourless, unilocular spores, while 
those types having pale brownish, bi- or quadrilocular spores are included 
in the genus Thelidium . In other respects both descriptions agree fairly 
well with V. margacea. 
This method of widely separating lichens which differ in the absence 
or existence of septate spores, but are otherwise closely similar, is unsound. 
The spores of V. margacea have been shown to be aseptate, uni- and tri- 
1 L. Univ., p. 286. 2 Ang. Lich., p. 52, Plate XXIV, Fig. 1. 
3 Lich. FI., p. 447. 4 E. Bot. Suppl. No. 2768. 
6 FI. Lapp., p. 4 66. 6 Syn. Meth. Lich., p. 93 ; L. Univ., p. 282. 
7 Mudd, Man. Brit. Lich., p. 294. 
8 Leight. Ang. Lich., p. 62, Plate XXVI, Fig. 3. 
