6. SPHAEROPHORUS Pers. Ust. Ann. 7: 23. 1794. 



On studying Sphacrop/ionts as typified by S. coralloides we find 

 some marked differences as compared with the foregoing genera. 

 The stipe and primary thallus (see discussion of primary and 

 secondary thalli, stipes and podetia in Cladoniaceae, p. 119) are 

 wanting ; the stipe is doubtless represented by the main stem and 

 its branches, but it has become enormously elongated, branching 

 dichotomously, and is entirely covered by the algal layer. The 

 stipes in association with the symbiotic algae have become converted 

 into a fruticose thallus ; that is, we find the conditions to be closely 

 analagous to those met with in Cladonia as will be seen upon a com- 

 parison of the two genera. In both the stipe or apothecial stalk has 

 become converted into a fruticose thallus ; in Sphacrop/ionis the 

 assimilating surface is materially increased by the formation of 

 numerous minute cylindrical branches ; these secondary branches 

 never bear apothecia ; in some species (S. fragilis} the distinction 

 between assimilating branches and apothecial branches is not so 

 marked, and in these forms it is found that apothecia rarely or never 

 occur, indicating that evolution is working toward the improvement 

 of the assimilative function and neglecting the spore bearing function 

 (see reproduction by spores, p. 90). The primary thallus has 

 entirely disappeared, its function being supplanted by the secondary 

 thallus. 



The apothecial and spore-characters at once indicate the true po- 

 sition of this genus. As already indicated the globose apothecia oc- 

 cur at the ends of the main branches, each branch bearing one 

 apothecium which is at first entirely enclosed by the thalline struc- 

 ture ; the paraphyses are slender, simple and few in number ; the 

 spore-sacs have the same general structure as in Acolium, but the 

 spores are simple with an enormously developed exosporium which 

 becomes blue-black at the time of maturation ; for some distance 

 the hypothecial hyphal tissue (2, f) is dark, due to coloring sub- 

 stance deposited in the cell-walls. 



The thallus (including main branches and secondary branches) 

 possesses a typical radial structure. On the outside occurs a smooth 

 brittle layer, consisting of hyphal cells usually extending vertically 

 to the longitudinal axis. The cell-walls are so much gelatinized that 

 it is almost impossible to recognize the outline of the individual cells. 

 Internal to this layer occurs the algal layer consisting of a loose net- 



