SPORE-PRODUCING MEMBERS 327 
there is thus evidence of great fluctuation in size of the sporangia, and 
though the presence of the sterile trabeculae indicates that the limits of 
convenience as regards nourishment and mechanical support are approached, 
still there is no evidence that within the Lycopodinous phylum (as now 
limited by the exclusion of the Psilotaceae) any actual septation has 
occurred. The relation of one sporangium to each sporophyll, and no 
more, is maintained throughout with some rare exceptions, which as they 
never became characters of a race may be held as abnormalities. There 
is, moreover, no evidence of interpolation of sporangia, those which exist 
are all found to arise in strictly acropetal order. 
Finally, it would seem probable that the heterosporous condition, where 
it occurs, supervened after the individual sporangia had already acquired 
approximately the dimensions and characteristics seen in the different types 
in which it appears. 
