Germinating Spores in a Fossil Fern. 2 1 
The three spores, B, C and D, which are shown in juxtaposi¬ 
tion as they actually occur (cf. Fig. 60), present other stages of 
germination. The spore B (72/x in greatest diameter) has produced 
a thick outgrowth, about 80/x long and 40//. thick in the middle part; 
it has split away somewhat on one side from the spore-membrane, 
and is cut off by a septum which is partly displaced towards the 
cavity of the spore. The outgrowth itself appears to consist of 
three cells, of which the middle one is very short (13-5/x). Both the 
transverse lines appear to represent genuine septa, though the 
frequency of cracks in the matrix 'demands caution. The lowest 
septum, which is somewhat broken, is undoubtedly a true cell-wall. 
The whole outgrowth is clearly a young stage of the prothallus. 
Spore C, though slightly damaged, shows a very evident case 
of prothallial development. The outgrowth at its base is of the 
full width of the spore, from which it is separated by a septum, 
while a second transverse wall divides it into two parts of nearly 
equal length. At the narrow end of the young prothallus a rhizoid 
has grown out at a sharp angle ; it abuts on the end-wall of the 
prothallus of B, and has somewhat indented it (Fig. 61, C, r). The 
arc of thick cell-wall seen in the angle between rhizoid and 
prothallus is probably a fragment of the exospore. 
Spore D appears to have been more advanced in germination 
than the others. Here the outgrowth, measured from the septum 
dividing it from the spore cavity, is about 85 /x long, but it appears 
to be incomplete. It consists of two cells, or three if we include 
the spore. The septa between the cells have partially split, and 
the last cell, from its form, could not have been really terminal, but 
one or more cells would appear to have been lost. A rhizoid ( r ) 
is seen, closely applied to the spore and prothallus ; it takes a 
curved course, so that its upper and lower walls are partly seen in 
surface view ; the attachment of the rhizoid to the prothallus does 
not lie in the plane of section. 
These four examples may serve to illustrate sufficiently the 
stages of germination observed. A large number of other germi¬ 
nating spores are present in the sporangium, as will be seen on 
examining Fig. 60, where some of the clearer cases are lettered ( g ), 
showing rhizoids and young prothalli. At several places the small 
round transverse sections of rhizoids are seen, belonging no doubt 
to germinating spores not seen in connection with them. As 
mentioned above it is not unlikely that every spore left in the 
sporangium had started growing. 
