English Soils : an Important Factor in Soil Biology . 5 1 
stages in the development and life-history of a number of the species found. 
This is especially true of the germination and development of some of the 
blue-green algae, which in some cases have seemed somewhat obscure. In 
these cultures two quite different methods of germination were observed, 
a direct germination into a more or less typical vegetative plant and 
germination into what can only be regarded as a juvenile form bearing none 
of the characters of the adult plant. The former appears to be by far the 
more general method of germination and may be subject to slight variation 
in details (Text-fig. 3 , A-D) ; the latter is largely found in the genus 
Nostoc (Text-fig. 3, E and f). 
In Nodularia Harvey ana (a) and in Anabaena oscillarioides forma (b) 
a single transverse division of the protoplast of the spore appears to take 
place before the wall is ruptured ; some part of the wall then becomes 
diffluent and the free end of the filament is gradually protruded through the 
aperture as a result of the succeeding divisions of the young cells. The end 
of the filament remaining within the spore in Nodularia Harveyana may 
remain in this position until the filament has attained a length of more than 
twenty cells, though in other cases short filaments of not more than six cells 
have been observed quite free from the spores which produced them. The 
young filaments soon become broken up into hormogones terminated by 
heterocysts. The spores were frequently observed to germinate in the 
cultures while still in series, without the interposition of a resting period 
after formation. 
In Anabaena sphaerica (c) the spores were also observed to germinate 
immediately after formation and while still in series, but in this case at least 
four transverse divisions of the protoplast were effected before the cell-wall 
was burst open. Later the end of the spore became gelatinous and the 
young filament was protruded through the aperture. The basal cell soon 
became converted into a heterocyst and remained for a considerable time 
within the old spore-cavity, while the free end extended farther and farther 
from the spore as a result of succeeding divisions of the young cells. 
In Cylindrospermum licheniforme (d) the end of the spore was observed 
to open as a lid to permit the extrusion of the young filament. Several 
divisions of the protoplast took place before the wall was ruptured, and it 
sometimes, though not always, happened that a doubling of the filament 
took place so that both ends of it were protruded at once through the 
terminal aperture, as shown in the figure. 
In Nostoc commune (Text- fig. 4) a rejuvenescence of the protoplasm 
appeared to take place inside the spore, with the result that the spore-wall 
burst and the contents were extruded either immediately or after a single 
division within a mucilaginous envelope formed from the inner layers of the 
spore-wall. In most cases this aperture was produced by a dissolution of 
part of the wall, but in a few cases a circular portion of the wall was 
