The Morphology and Ecology of an Extreme Terrestrial 
Form of Zygnema (Zygogonium) ericetorum (Kuetz.), 
Hansg. 
BY 
F. E. FRITSCH, D.Sc. 
With three Figures in the Text* 
T HE Alga Zygnema ericetorum (Kuetz.), Hansg. has long been familiar 
as a form capable of inhabiting both terrestrial substrata and pieces 
of standing water, but until recently it had received little attention. West 
and Starkey (’ 15 ) have, however, in the present year, added considerably to 
our knowledge of the Alga in question. 
The present communication is mainly concerned with a form of 
Zygnema ericetorum that inhabits certain bare areas on the Hindhead 
Common (cf. Fritsch and Salisbury, ’ 15 , p. 131). The habitat is as inhos- 
pitable as could well be imagined and, as a result, the characteristics usually 
found in the terrestrial form of the Alga are developed to a very pro- 
nounced extent. Certain of these characters appear as adaptations to the 
habitat (see especially the third section of this paper). 
Apart from what I will in the following pages refer to as the Hindhead 
form, I have also examined material of the ordinary terrestrial form from 
the foot of the scree below the cliffs of Lliwedd on the Snowdon Range, 
and of the aquatic form from Frensham in Surrey. For the former material 
I am indebted to Mr. R. J. Tabor, B.Sc., whom I have also to thank for 
certain details as regards its habitat. 
As far as I am aware, only one other member of the Zygnemaceae 
occurs on terrestrial substrata, and that is Zygnema javanicum, v. Martens 
(De Wildeman, ’ 97 , pp. 82, 83), since Z. pachydermum, W. and G. S. West, 
has recently been stated not to be specifically distinct from Z. ericetorum 
(cf. West and Starkey, T 5 , p. 203). The latter species enjoys a very wide 
geographical distribution, having been recorded from many different parts 
of the world, and, in view of its apparent variability, it is not altogether 
out of the question that Z. javanicum may be another form of this 
ubiquitous Alga. 
[Annals of Botany, Vol. XXX. No. CXVII. January, 1916.] 
