24 PROCEEDINGS OF THE AMERICAN ACADEMY 



breaking down and absorj)tion of the membranes between adjacent 

 cells. This lysigenetic process is continued until a pore is formed 

 piercing the cortex, and occupying the centre of a slight elevation on 

 the surface caused by the expansion and upward growth of tlie young 

 spermogonium. Meanwhile, before the formation of the pore, the 

 central part of the spermogonium has become hollow by absorption, 

 and the space thus left becomes, in the mature spermogonium, almost 

 filled with stout, branched, multicellular branches of the hyphfe form- 

 ing the wall ; on the joints of these — the so-called arthrosterigmata — 

 are borne the minute spermatia in vast numbers. As yet I have been 

 unable to secure the youngest stages in the development of the apothe- 

 cium, but much may be inferred from stages already rather advanced. 

 To the naked eye these appear as slight elevations on the ribs, closely 

 resembling the mature spermogonia, except that they are a trifle 

 larger, of a dark brown color, and present no trace of an orifice at the 

 top. In section they are seen to be spherical masses of very delicate 

 densely interwoven hypha3 about 0.3 mm. in diameter, occupying the 

 upper part of the medullary layer, displacing the algae immediately 

 above them, and covered by the brown cortex. The lower half of one 

 of these hyphal knots is permanent, and retains its dense hyphal struc- 

 ture, but the upper half soon becomes disorganized, the hyphse com- 

 posing it being partially absorbed, leaving a hemispherical cavity, from 

 the upper part of which the broken ends of the original hyphoe may be 

 seen hanging down into the cavity. Meanwhile, as the cavity forms, 

 the permanent tissue beneath gives rise to a series of delicate parallel 

 threads which grow upwards into the cavity, and we thus have formed 

 a young hymenium imposed upon a dense subhymenial layer, which 

 owes its origin to a copious branching of ordinary medullary hypha3. 

 Treatment with iodine, or with chloro-iodide of zinc, has the effect 

 of coloring both the subhymenial layer and the young paraphyses a 

 deep yellow, darker and more pronounced than the color imparted to 

 the ordinary hyphte of the medulla. But no blue coloration is as yet 

 visible in any part of the structure, nor is there any sign of a tricho- 

 gyne even in this early stage, or of anything which might pass for an 

 ascogenous system of cells in the subhymenial layer. The young liy- 

 menium increases rapidly in size by the interposition of new paraphy- 

 ses as well as by the branching of those already formed, until one of 

 two things occurs : either the increase in area of the hymenium 

 takes place over its whole extent, until the tension upon the cortex 

 becomes too great, and the latter is ruptured over the whole disk ; or 

 else, in cases where the apothecium arises in the gonidial layer imme- 



