152 OLAF GALL®E 
away at the base; (3) procumbent, dorsiventral, hapteron-producing 
podetia, dying away at the base behind; (4) procumbent, dorsiventral, 
hapteron-free podetia, dying away at the base behind. 
Type 1 is found only in the hypothallus-wanderers, and in the 
majority of these. 
Type 2 is found in some of the hypothallus-wanderers, and in 
all the podetium-wanderers. As a rule, we may take for granted 
that podetia of type 1, when they become old, ultimately pass over 
to type 2 for a short time, before they die away entirely. But even 
if the boundary line between the two types is thereby made very 
uncertain, it is advisable to maintain both of them, as there are 
undoubtedly species which never die away below or, at any rate, 
very rarely do so (e. g. Sfereocaulon condensatum, Cladonia papillaria, 
C. pyxidata, C. pityrea and possibly others). 
Type 3 like type 4 is commonest in the podetium-wanderers, 
in which the edge of the tuft usually grows in circumference by 
the marginal podetia lying down and creeping over the surface of 
the ground, and like runners spreading out on the substratum. By 
this the podetia often become somewhat dorsiventral and, in addi- 
tion, send in some cases haptera into the ground (the majority of 
the podetium-wandering Cladonias); in other cases nothing like this 
happens (Stereocaulon, Dufourea). 
Consequently, in the same tuft and in the same species more 
than one type of podetium may be found, so that types 1 and 2 
are united, in that the old podetia may belong to type 2, and the 
young, on the other hand, to type 1; but, as already mentioned, 
in some species type 1 is the dominant one. 
Types 2 and 3 are, as a rule, united in the same species and 
in the same tuft, in that type 3 forms the runners of the tuft, and 
type 2 the old erect shoots in the middle of the tuft. 
In the same way, types 2 and 4 are as a rule united in the 
same tuft. 
It is evident, that all species which have on the whole erect, 
permanent podetia, are less adapted to grow on the earth, because 
they are so dependent on the substratum for their attachment, and 
are therefore easily overgrown and crowded out by other species. 
Their apical growth also is very limited, which in ne reduces 
their capacity for competition. 
Podetium-wanderers, on the other hand, are excellent compe- 
titors. With regard to these I shall add some further notes about 
