502 FILICALES 
this species that the incipient stages of germination have been observed 
within the sporangium, a fact held to show its Fern-nature, while its 
other characters relate it to the Botryopterideae. 
The sporangia have been successfully observed in Zygopteris by Renault 
(Fig. 272). They were borne in groups on the ends of the pinnules, 
and were pear-shaped and slightly curved. The stalk, though elongated, 
was fairly robust, and widened gradually into the sporangial head. The 
latter was composed of at least two layers of cells, the inner of which was 
Fic. 271. 
Stauropteris Oldhamia, Binney. A =sporangium in nearly median section, attached 
terminally to an ultimate branchlet of the rachis; s¢=stomium. Scott. Coll., 2213. 
#=sporangium in tangential section attached to a short piece of a branchlet. Scott. 
Coll., 2207. _C=sporangium with wall burst attached as before. =palisade tissue of 
branchlet. Scott. Coll., 2219. All figures Xabout 50. (From sketches by Mrs, D. H. 
Scott. The specimens are from Shore, Littleborough, Lancs.). 
transient, while the outer remains as the mature sporangial wall. This 
is differentiated to form the annulus, which appears as a broad band 
composed of several rows of deep cells, with indurated walls, and ran 
along either side of the sporangium from base to apex; the remainder 
of the wall is composed of smaller, elongated cells. The mechanical 
annulus thus composed of several rows of cells, forming a broad marginal 
band or hoop, resembles the similar structure seen in the sporangium 
of Angiopterts (see below, pp. 515-16). The spores are numerous: a rough 
estimate from the transverse and longitudinal sections drawn by Renault 
points to an output of 500 to 1000 spores in each full-sized sporangium : 
but there is considerable variation in the dimensions of the sporangia. 
