134 Scientific Proceedings, Royal Dublin Societij. 



Its presence is, however, enough to prevent one from confusing the resting 

 spores of Clirysophlyctis with those of Urophlijctis leproides — the cause of beet- 

 tumour, a mistake which lias unfortunately crept into mycological literature. 

 As a rule there is only one resting sporangium in a host-cell ; occasionally 

 there are two. 



Through the dark wall of the sporangium one can see the spongy or 

 granular protoplasmic contents enclosing in the centre a bright body which 

 reagents show to be a large reserve fat globule. 



Tlie origin of these resting spores can be traced in microtome preparations 

 (PI. X., figs. '6, 4, 5). The naked dense plasmodium soon becomes wholly 

 converted into a sporangium which continues to enlarge and to occupy more 

 and more of the enlarging host-cell. Chrysophlyctis is thus holocarpic, and 

 differs from the eucarpic Urophlyctis, in which the whole of the vegetative 

 body is not used up in the production of the propagating organs, as is the 

 case in Chrysophlyctis. 



I followed the resting spore from its foundation to complete maturity, but 

 must leave to a future occasion an account of the nuclear and other changes 

 in the developing sporangium, as my results are not yet complete. I may say 

 there are not wanting signs that the small host-cells surrounding the invaded 

 enlarged one may lose their cell-walls in part, and form a sort of symplast 

 round the developing sporangium. 



Germination of Eesting Sporangium (or " spore "). 

 Judging from analogy and from the examination of preserved sporangia, 

 I concluded the " resting spore " must be a composite body or resting sporan- 

 gium (PI. XI., fig. 4). I proceeded to try and rouse it from its winter rest by 

 stimulating solutions of one kind or another, e.g., by : — A, 1 per cent, sugar, 

 B, 2 per cent, sugar, C, A or B with a trace of theproteid ferment papayotin, 

 D, potato juice alone ; and E, D with papayotin. Cultures in these and in 

 water were kept, as well as macerations, in darkness, in light, at room 

 temperature, and in the incubator at a constant temperature of 20° C, and 

 examined from day to day. I constantly found empty spore-cases with 

 ruptured walls, but for some time failed to see any signs of escaping zoo- 

 spores. At last the potato juice, exercising possibly a chemotactic influence, 

 gave success ; and sporangia with split walls and escaping zoospores were found 

 (PI. XI., fig. 6). These showed the same sluggish movements observed in the 

 sporangia of certain other Chytridians, disturbed during their resting period. 

 Each sporangium contains hundreds of more or less pear-shaped uniciliate 

 zoospores. As the zoospores are being formed, the large central fat globule 

 disappears, being broken up iuto innumerable minute globules which are 



