[Vol. 9 



88 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



Where the sporangium wall is exposed, it, as well as the adja- 

 cent epidermal tissue of the leaf base, may show wall thickening 

 in groups of cells, resulting in a brown-spotted effect under 

 magnification. When the( patches of brown sclerenchymatous 

 cells are very numerous, the brown coloring is readily noted; an 

 extreme case is found in /. melanopoda Gay & Dur., where the 



specific name is derived from the deep coloring of the bases of the 

 leaves. 



The sporangia are of two sorts, occurring in the same plant, 

 though in some cases at different seasons. A striking example 

 of probable difference in time is found in the East Indian form. 

 The description of /. coromandelina L. fil. and /. brachyglossa 

 A. Br. both left the condition of the microspores and micro- 

 sporangia in doubt because of the failure to obtain microspor- 

 angiate material. In a collection sent from India through the 

 courtesy of Dr. W. S. Dudgeon, all the sporangia appeared to be 

 megasporangiate. Yet with diligent search about the bases, 

 among old megaspores, microspores, probably from the previous 

 season, were found. 



The sporangia of the two kinds have been found to originate 

 and pass through their early stages in similar fashion (Bower, '08, 

 Wilson-Smith, '00). It is only in later development, and es- 

 pecially at maturity, that the heterosporous nature becomes 

 striking. The sponmgium initial is a transverse row of super- 

 ficial cells, which by periclinal divisions, give rise to wall layers 

 and to a sporogenous mass. The velum may be derived from a 

 part or the whole of the upper tier of cells arising from the 

 division of the initial cells (Wilson-Smith, '00). According to 



the results of Scott and Hill, the velum arises from the tissue 

 between the ligule and the sporangium initial. The growth here 

 in the "sella," a term given by A. Braun, first gives the labium 

 by upward growth, and then the velum by downward extension. 



Bands of cells in the sporogenous region become sterile, form- 

 ing the traheculae, eventually more or less plate-like cross exten- 

 sions into the spore mass, bordered by a tapetal layer (Wilson- 

 Smith). The trabeculae are unusually large and distinct in the 

 megasporangia, in which some of the potentially sporogenous 

 colls develop at the expense of others. The large functional 

 ones produce tetrads of megaspores, whereas in the micro- 

 sporangia, all the sporogenous mass, except the trabecular strips, 

 produces microspores. 



