5 .8 



F1LICA1 ES 



marked a feature in l-'erns at large thai those irregularities eomuund the 

 greater attention. Fig. 286 A represents a tangential section traversing 

 three sori in A///,/ e//iptiui, of an age prior to the tetrad division : the 

 varying size of the sporangia is striking, as also their frequent grouping 

 in pairs, separated by a thin, or even by a partial septum. Sonu 



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 ft Oli 



f*t*tfffltffllft1 



ft ft! Hi 



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ftwMMM *Uiftic*, Smith. Drawings illustrating partial septations of the : 

 I, tangential section through three sori, showing the loculi in ground plan : i 

 ftcn thin, so that pairs of loculi are in close juxtaposition ; the loculi 



_ 



.4. tausential section through three sori, showing the loculi in ground plan : the sepia we 

 often thin, so that pairs of loculi are in close juxtaposition ; the loculi marked (.r) 

 are large, and show one or more partial septa, x ao. 0, C, />, /t, show such locuti with 

 jvmiaf septa in greater detail : in /> and E it is difficult to decide whether the cells 

 marked (?) will develop as tapetum or as spore-mother-cells. X 150. 



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these partially septate sporangia are represented more in detail 

 Figs. 286 B-E, From these drawings it is dear that the identit 

 sporangium is not maintained: that where the initial sporogenous group 

 is large, some of its cells may develop as transitory tapetum, o; 

 permanent cells of septal tissue : and thus various intermediate step- 

 completion of a septum may be observed. Somewhat similar eond 



