272 



MOSSES AND FERNS 



CHAP. 



archesporial groups of cells corresponding to the separate 

 chambers found in the complete synangium." The whole 

 process takes, according to his account, about six months. 

 Luerssen was unable either in Marattia or A^tgiopteris to trace 

 back the archesporium to a single cell, which Goebel ^ claims is 

 present in the latter. 



In Angiopteris the process begins as in Marattia, but at a 

 period when the leaf is almost completely developed and 

 unfolded. The first indication of the young sorus is the 



Fig. 143. — Angiopteris evecta (HofFm). Development of the sporangium. A, Vertical section of very 

 young receptacle ; B, similar section of an older sporangium in which the archesporium is already 

 developed (after Goebel) ; C, longitudinal section of an almost fully-developed sporangium, showing 

 the persistent tapetal cells (t); r, the annulus, X75. 



formation of an oblong depression above a young vein, and 

 about the border of this are numerous short hairs, which as a 

 rule are absent from the epidermis of the leaf (Fig. 143, A). 

 The placenta is formed as in Marattia, but instead of the two 

 parallel ridges that are found in the latter, the young sporangia 

 arise separately, much as in Botrychiiim. As in the latter too, 

 Goebel states that the archesporium can be traced to a single 

 hypodermal cell in the axis of the young sporangium. This 



1 Goebel (3). 



