30 PEOCEEDINGS OF THE AMERICAN ACADEMY 



In the tballine structure of the species before us, we find so marked 

 a resemblance to that of Sticia anthraspis, that we may pass at once 

 to a brief consideration of the origin and growth of the apothecium. 

 As is well known, the large, peltate apothecia occupy rather sparincrly 

 the lower surface of the extended lobes, and it is a matter of some 

 difficulty to obtain the earliest stages in the development of the fruit. 

 By making careful longitudinal sections, however, through the tips of 

 the thallus lobes, I was enabled to see more or less plainly the oinffin, 

 and to trace the later development, of the apothecia. The first sign of 

 the coming apothecium is the appearance of a small spherical knot of 

 hyphge arising from the medullary hypha;, and occupying a position 

 immediately below the algal layer, which, at the margin of the thallus, 

 is very thin and composed of only scattered colonies. The primordium 

 never occupies the exact tip of the margin in section, but inclines more 

 or less toward the lower surface, sometimes, indeed, arising from the 

 medullary layer beneath the lower cortex and at some distance from 

 the margin. The few algal colonies which do occur between the pri- 

 mordium and the lower surfece of the thallus are pushed aside by the 

 growth of the former, which then remains covered only by the cortex. 

 Before the cortex is disintegrated or ruptured, the young paraphyses 

 arise as perpendicular branches of the knot of hypha?. No part of the 

 knot, or of the paraphyses arising from it, is colored blue by iodine, 

 but the whole gives homogeneously the ordinary protoplasmic reaction. 

 The growth of the young hymenium by the interposition of new para- 

 physes is equally rapid over the whole area, so that the cortex cover- 

 ing it is stretched more and more, and finally ruptured simultaneously 

 over the whole disk. The hymenium then increases even more rapidly 

 than before,' relieved of the tension of the cortex, and if it does not al- 

 ready occupy the lower surface of the thallus, the addition of paraphy- 

 ses is more in that direction, and by the time the young apothecium is 

 distinctly visible to the naked eye, it is seen to occupy entirely that 

 position. Often four or five young apothecia arise in such close prox- 

 imity to one another, that, in the ordinary course of growth, the inter- 

 vening tissue is broken down, and one large apothecium results. 



A section of the young apothecium exhibits a margin of extremely 

 simple structure, if indeed it can be called a margin at all. By reason 

 of the pressure exerted by the growing hymenium upon the investing 

 cortex, the cells of the latter are lengthened considerably in the direc- 

 tion of hyphal growth, i. e. perpendicular to the surface ; those hyphjB 

 of the cortex which are in direct contact with the paraphyses become 

 distinguishable from them only by their greater diameter, and the 



