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 



FIG. 271. 



Stauropleris Oldhamia, Binney. A sporangium in nearly median section, attached 

 terminally to an ultimate branchlet of the rachis ; $ = stomium. Scott. Coll., 2213. 

 B = 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 X about 50. (From sketches by Mrs. D. H. 

 Scott. The specimens are from Shore, Littleborough, Lanes.). 



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 Angiopteris (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. 



