34 
Colorado Experiment Station. 
flask. No algae appeared in sample No. 17, a raw soil from an 
adobe hill. Lack of mositure is undoubtedly an unfavorable factor 
in this case. In this connection, it should be said that cultivation, 
resulting in better aeration of the soil, is unquestonably favorable 
to increased activities of soil algae as well as other soil organisms. 
I can ascribe no reason for the non-occurrence or non-development 
of algae in Sample No. 3, a sandy loam from an orchard. It must 
be understood that the conditions under which all samples were 
grown were similar. It will be seen from Table I that the most 
prevalent species of algae in the 22 soil samples are Phormidium 
tenue, Nostoc “A”, Nostoc “B”, Nostoc commune, Anabaena “A”, 
N0dularia harveyana and Stigonema sp. These not only occur in 
a greater number of samples, but they form, as a rule, the greater 
portion of the algal mass in the flasks.. 
DESCRIPTION OF SOIL CAPILLARITY TUBE. 
Air. V. M. Cone, irrigation engineer in this Station, called our 
attention to the appearance of an abundant growth of algae in some 
soil tubes used in testing capillarity. One of these was chosen for 
examination of the algae it contained. 
The soil, a sandy loam, had been replaced foot for foot in a 
tube, 1 inch in diameter, making a 5-foot column. The tube was 
placed in the laboratory about one foot from a wall, hence the algae 
grew only on the lighted side. Unfortunately, no data were se¬ 
cured as to the date of appearance of the algae, although it is known 
that development was first conspicuous in the third foot of soil. 
Finally, the first two feet exhibited the greatest development. There 
was algal growth, however, in every foot of soil except the fifth. 
It is not to be understood by this that algae grow at a depth of 4 
feet or even 1 foot below the soil surface. It is very probable that 
surface waters continually carry spores ^from upper to lower soil 
layers; there the spores remain quiescent for a short period, 
finally dying unless favorable conditions are restored either by na¬ 
tural or artificial means. Extreme precautions are necessary in 
taking samples to prevent contamination of one soil layer with an¬ 
other. Again, it is essential that the tubes or vessels containing 
the soil, be previously sterilized ; dust sticking to the sides may be 
a possible source of contamination. By a glance at the soil capil¬ 
larity tubes showing algae growing in the first four feet, one might 
gain the notion that they grew at such depths under field condi¬ 
tions. Yet when the above possible sources of contamination of 
the lower soil layers are considered, the appearance of algae in 
the lower layers of the tubes in question, looses its significance. 
The algae occur in the capillarity tube in patches ranging in 
size from mere specks to areas one or more inches in diameter. 
(Plate IV., fig. 1). The patches are, for the most part, irregularly 
circular in outline. The yellowish-green to reddish areas are 
Plcurococcus; the dark-green areas are mostly Oscdlatoria formosci 
