An OLAF GALLGE 
Cetraria cucullata Bell. Peltigera aphtosa L. 
— hiascens (Fr.) Th. Fr. — canina (L.) Fr. 
— nivalis (L.) Ach. — horizontalis L. 
Dermatocarpon cinereum Pers. = lepidophora Nyl. 
— hepaticum Ach. — malacea (Ach.) Fr. 
— rufescens Ach. — polydactyla(Neck.)Hoffm. 
Leptogium lacerum Ach. — rufescens Fr. 
— scotinum Ach. _ venosa (L.) Hoffm. 
Nephroma arcticum L. Physcia pulverulenta Nyl. 
— expallidum Nyl. (v. muscigena). 
— tomentosum (Hoffm.) Nyl. Solorina bispora Nyl. 
Pannaria microphylla Nyl. — crocea Ach. 
Parmelia lanata Wallr. — saccata L. 
The Fruticose earth-lichens. Three types may be distin- 
guished, which are however connected by intermediate forms, 
namely, Hypothallus-wanderers, Podetium-wanderers and 
Primary-scale-wanderers, which have been exhaustively des- 
cribed and for the first time established by me in 1913. From 
these groups I quote as examples: — 
Hypothallus-wanderers: Stereocaulon condensatum, Cladonia 
papillaria, C. pyxidata, C. pityrea, C. fimbriata, C. squamosa, C. cris- 
pata, C. cornuta, C. macilenta, C. Floerkeana, C. coccifera, C. deformis, 
C. verticillata (see figs. in Forb. Unders., 1913). 
Podetium-wanderers: Stereocaulon tomentosum, S. evolutum, 
S. coralloides, S. paschale, Dufourea arctica, D. muricata, Siphula cera- 
tites, Cladonia degenerans, C. gracilis, C. furcata, C. rangiformis, C. un- 
cialis, C. rangiferina, Thamnolia vermicularis, Alectoria ochroleuca, 
Cornicularia aculeata, Bryopogon jubatus v. nitidulus, Spherophorus 
fragilis (see figs. in Forb. Unders., 1913). 
Primary-scale-wanderers: Cladonia foliacea (see figs. in 
Forb. Unders., 1913). 
As an example of the structure of a hypothallus-wanderer, 
a description of Cladonia pyxidata will suffice. When the spore in 
this species germinates, it gives rise to a mycelium which spreads 
out radially in the ground (Dan. Lik. Ok., fig. 39 a), and is called a 
hypothallus. Wherever these purely mycelial hyphæ encounter Pleuro- 
coccus-algze on the surface of the ground, they establish -— as has 
already been described by Krabbe (1891) and Wainio (1898), — 
a connection with these latter, and form lichens. We may then, on 
a somewhat older hypothallus, distinguish between the purely my- 
celial hyphæ, which have not as yet begun their lichen-formation, 
and within these (nearer to the germinating point) a belt, where the 
