206 



THE MARATTIALES 



case and that the tapetal cells persist until the division of the spores is complete. 

 Bower has confirmed this statement and found that the same condition of things 

 obtains in the other genera. 



The most complete account of the development of the sporangium is that of 

 Bower (Bower 6), who has studied the development in all of the genera except 

 Archangiopteris. Except for the difference in form, there is no essential difference 

 in the development of the sporangia in Kaulfussta and Dancea from that found in 

 Marattia. In Danaa, however, the individuality of the loculi of the synangium 

 is less clear than in the other genera. Very often Bower found that the arche- 

 sporium became divided more or less completely by parts of the sterile tissue, some- 

 what in the same fashion that the so-called "trabeculae" are formed in Isoetes. 

 In Dancea, moreover, the synangium from the first is solid, and the cleft which is 

 present in the young synangium of Marattia is absent. In Kaulfussia the develop- 

 ment of the synangium differs in that a single circular ridge is formed instead of the 



Fig. i86. 



A. Section of a young synangium of Marattia fraxinea. X225. 



B. Loculus from an older synangium. >, tlie tapctum (after Bower). Xl 



um 



two parallel ones found in Marattia, and the loculi or chambers of the synangi„... 

 are thus arranged in a circle around a central pit-like depression. Bower states 

 that the sporogenous tissue of each loculus in all the forms he examined can usually 

 be traced to a single mother cell. He also found that the tapetum always arises 

 from the cells adjacent to the archesporium, and that normally all of the sporogenous 

 tissue develops into spores. In these respects the Marattiaceze closely resemble 

 Helmtnthostachys and Botrychium. 



In Danaa and Kaulfussia there is no mechanical tissue representing the annulus 

 found m the more specialized ferns. The dehiscence of the sporangium in these 

 forms IS brought about merely by a shrinking of the cells on either side of the slit by 

 means of which each loculus opens. This slit is very short in Dancea and may finally 

 appear as a circular pore, but it is not essentially different from the more elongated 

 sht found in Kaulfussta and Marattia. In the latter there is developed, in the outer 

 tissues of the synangium, mechanical tissue which causes the two halves of the 

 synangium to separate, very much like the two covers of a book, and the elongated 

 s It from each loculus opens into this space between the widely separated halves of 

 the synangium. 



