On the Alga-Flora of some Desiccated English Soils : 
an Important Factor in Soil Biology. 
BY 
♦ 
B. MURIEL BRISTOL, M.Sc. 
With Plate II and twelve Figures and three Tables in the Text. 
Synopsis. 
PAGE 
I. Introduction 35 
II. Cultural Methods .37 
III. Results of Cultural Experiments 39 
IV. Discussion of the Possible Significance of Algae and Moss Protonema in 
the Economy of the Soil 54 
V. Descriptive Notes on the Species found . 59 
VI. Summary 79 
I. Introduction. 
D URING recent years a good deal of attention has been paid to the 
activities of certain soil-organisms, with regard to their significance in 
the economy of the soil. Proceeding from the wonderful discoveries of 
Pasteur on bacterial fermentation, Berthelot in 1885 established the fact 
that the building up of nitrates in the soil is due to the activities of certain 
micro-organisms. This discovery led to wider experiments in all directions, 
and especially to the investigations of Hellriegel and Wilfarth in connexion 
with the nitrogen supply of leguminous plants, and of Winogradsky and 
Beijerinck on the work of nitrogen-fixing bacteria in the soil. 
These activities mark the beginning of a new era in biology, and have 
led to the establishment of a special branch of the science, soil biology, 
dealing with problems of interest not only to biologists but also to practical 
agriculturists. The activities of the nitrogen-bacteria of the soil are now 
well established, while those of the attendant soil-protozoa have already 
received a considerable amount of attention ; and the pathogenic effect on 
higher plants of nematodes, myxomycetes, bacteria, and fungi occurring in 
soils is studied as a special branch of plant pathology. The algae of soils 
have, on the contrary, possibly on account of their supposed lack of 
importance as factors in the economy of the soil, been almost entirely over- 
[ Annals of Botany, Vol. XXXIV. No. CXXXIII. January, 1920.] 
