736 
AZOLLA FILICULOIDES LAM. 
contains only one macrospore, which fills the cavity. At 
maturity, a transverse dehiscence liberates the spore, which 
sinks, and carries with it the upper part of the indusium 
attached as a conical cap. The lower globular part of the 
spore is filled with protoplasm ; the upper part has a very 
complex structure, which consists principally of three irregular 
pear-shaped bodies of cellular substance similar to the massulae, 
suspended around a central cone of the same material. At the 
apex there is always to be found a group of cells, which 
Campbell recognized as the resting cells of Anabcena azollce ; 
the alga is associated with the archegonium in the young state, 
and as the indusium grows up around it and finally closes the 
apical orifice, the entrapped algal cells pass into the resting 
state and lie dormant within the spore until the cotyledon 
emerges, when they renew their activity. In A. filiculpides 
the spore wall is heavily warted and a felt of fine threads, 
which connects the protuberances, serves as a grip for the 
glochidia of the massulae, by means of which the two kinds of 
spores are held together. In cultivation, the least disturbance 
of the aquarium brings the spores into contact with each other, 
and it may be presumed that, in statu natures, disturbance of 
the bottom by water currents, animal agency, etc., produces a 
similar result. As many as three hundred macrospores have 
been seen in one mass measuring 15x3 m.m., so tenaciously 
held together by the glochidia of many hundreds of massulae 
that it could be handled with forceps without disintegration. 
The young sporophyte gradually pushes through the episporium, 
thrusts aside the cap and comes into view, either bringing the 
spore to the surface or detaching itself and assuming an 
independent existence. The full significance of the spore 
structure is not as yet understood. After working with dried 
material, which floated buoyantly, Strasburger expressed the 
opinion that the spongy substance forming the massulae and 
the episporium constituted a floating apparatus intended to 
bring the spores to the surface on liberation from the mother 
plant ; but Campbell has correctly shown that, under normal 
conditions, the macrospores and massulae do not rise. 
