B. Muriel Bristol. 
138 
which the soils were to be introduced. 1 The culture solution was 
placed in the sterilised vessel to a depth of about half-an-inch, and 
about 2 or 3 c.c. of the soil to be examined were then introduced 
into the solution by means of a sterilised spatula. The vessel, 
closed with its lid or cotton-wool plug, was then placed under a 
glass case to keep the dust from accumulating on its surface. 
The culture medium used was a mineral salt 
sisting of:— 
solution con- 
Potassium dihydrogen phosphate (KH 2 P0 4 ) 
10 gm. 
Sodium nitrate (Na N0 3 ) 
10 gm. 
Magnesium sulphate (Mg S0 4 ) 
•3 gm. 
Calcium chloride (Ca Cl 2 ) 
•1 gm. 
Sodium chloride (Na Cl) 
•1 gm. 
Ferric chloride (Fe Cl 3 ) 
•01 gm. 
Distilled water ... 
1000 c.c. 
Owing to unfavourable conditions of climate, viz., short days 
absence of sunlight and low temperatures, growth in the cultures 
was very slow, and it was not possible at the time of writing to 
make a complete and systematic examination of them. A few 
blue-green algae had begun to appear, but the most interesting fact 
was the growth of moss protonema from certain of the soils obtained 
from the Rothamsted Experimental Station. The protonema first 
appeared in the form of a few fine green threads growing from a 
particle of soil; the threads rapidly branched until they became 
easily visible to the naked eye as tufts of varying sizes. The soils 
in which the protonema was observed were Barnfield 1870, Hoosfield 
1868 and Agdell 1867, so that it has been produced after prolonged 
drought, after 46, 48 and 49 years respectively; none was found in 
any of the Broadbalk soils nor in Geescroft 1865. 
Examined under the microscope, the protonema is seen to have 
the structure characteristic of any filamentous moss protonema. 
The cross walls are oblique throughout the length of the filament, 
and the outside walls are very thin ; the end cells are slightly 
tapering and rounded at the apex. Each cell of the filament contains 
a parietal layer of cytoplasm in which are embedded numerous 
small chloroplasts. Near the ends of the filaments the chloroplasts 
are disc-shaped, relatively small and fairly widely separated (Fig. 1, A), 
1 All the vessels, including small glass boxes and small conical flasks or 
wide-necked bottles fitted with plugs of cotton wool for stoppers, were heated 
three times in a dry steriliser to 120°-130°C, and kept at that temperature for 
about an hour ; the culture medium was heated three times in a steam 
steriliser for at least two hours on each occasion. 
