328 Howe: Observations ox the 



more completely in some respects than is indicated in the recorded 

 observations on that species. This practically complete series of 

 early stages in the development of the disc seems to confirm, with 

 much certainty, the morphological explanation of the disc put for- 

 ward by Count Solms-Laubach in 1895, and perhaps justifies car- 

 rying his idea a little further. The disc begins as a whorl of 

 ovoid protuberances, which are at first free from each other, though 

 in close juxtaposition. A little later, these processes become ob- 

 long-cylindrical or somewhat tongue-shaped in outline (Figs. 6-8). 

 The formation of the partial partition constituting the distal 

 boundary of the vestibule at the base of each process begins very 

 early (Figs. 6 and 7). In fact it seems to be formed almost simul- 

 taneously with the process itself, for we have been able to find no 

 stage so young as to show no trace of it. The next step is the 

 appearance of the rudiments of the two articulated sterile branches 

 (Fig. 8), which begin as dome-shaped protuberances at the apex 

 of the process. It is of interest that these protuberances com- 

 monly do not at first stand one in front of the other or in line 

 with the radius of the disc, as they usually seem to do at a later 

 time, but are almost side by side in line with a tangent to the 

 disc. And when, as rarely happens, three rudiments of sterile 

 branches appear instead of two, the three are never in a straight 

 line but form an evident terminal verticil. The later develop- 

 ment commonly thrusts them nearly into a radial line, but there 

 are some exceptions to this as will be seen from our Fig. 30. In 

 the course of time, each of these outgrowths becomes strongly 

 constricted in the zone of emergence from the body of the orig- 

 inal process and is at length in communication with it only by a 

 narrow slit which is bounded by a callus-like thickening of the 

 membrane. And this narrow slit is evidently closed in the scars 

 which remain after the fall of the sterile filaments. Closely fol- 

 lowing the appearance of the rudiments of the sterile branches, 

 the first indication of the origin of the sporangium may be recog- 

 nized. The sporangium begins as a rather broad out-pocketing 

 on the outer face of the original process at about its middle or 

 sometimes nearly as low as the basal third (exclusive of vestibule). 

 It is from the first broader than the rudiments of the sterile 

 branches and though it becomes somewhat constricted at its base 



