FILICINE/E LEPTOSPORANGIA TyE 



313 



granular contents usually, but not always, show the starch re- 

 action. The body of the free spermatozoid has the form of a 

 flattened band with thickened edges, which tapers to a fine 

 point at the anterior end, but is broader and blunter behind. 

 The peripheral cells of the antheridium become so much 

 compressed by the crowding of the sperm cells that they are 

 scarcely perceptible, but after the antheridium is burst open, the 

 two lower ones become so distended that they nearly fill the 

 central cavity. The opening is effected either by a central 

 rupture of the cover cell, or less commonly by a separation of 

 this from the upper ring cell. 



A 



Fig. T.i%.—Onoclea stnithiopteris (Hoffm). A, Longitudinal section of the apex of a female pro- 

 thallium, showing the apical cell {x) and a nearly ripe archegonium, X 215 ; B-D, development of 

 the archegonium ; longitudinal sections, X430 ; h, neck canal cell. 



The development of the archegonium is intimately connected 

 with the apical growth of the large female prothallium. As 

 soon as the single apical cell has been replaced by the marginal 

 initials, the divisions in the latter become very definite. Com- 

 parison of cross and longitudinal sections shows that these are 

 much like those of Marattia or, among the Hepaticae, Dendroceros 

 or Pellia epiphylla. Each initial cell has the form of a semi-disc 

 (Fig. 158, A), and the growth is both from lateral segments, 

 which mainly go to form the wings of the prothallium, and 

 basal, or inner segments, which produce the projecting arche- 



