36 On the Resting -Spores of certain Fungi. 



spores has not been observed. The whole process, however, 

 of their formation in the genus Gystopus is so precisely similar, 

 that we cannot err greatly in assuming that it must be much 

 the same in the two genera. 



The genus Gystopus comprises those parasitic fungi amongst 

 the Uredines, which are remarkable for their white spores, 

 Till the resting-spores of the different species were ascertained, 

 it was almost impossible to find good distinctive characters. 

 One species at least, Gystopus candidus, is to be found every- 

 where on the common shepherd's purse, where it is often 

 accompanied by Peronospora. parasitica. It is also frequent on 

 turnip leaves, cabbages, and other Cruciferae. The acrospores, 

 or conidia, which spring from the swollen threads of the my- 

 celium, form necklaces, as in O'idium, the joints of which give 

 rise to zoospores, as first observed by Prevost, in 1807. Like 

 those of Peronospora, they move about in water by means of 

 two lash-like appendages. Like them also, they germinate 

 when placed in water, and when resting on the leaves they 

 make their way by means of a germinating thread into the 

 subjacent tissues, which, as in most Peronosporce, throws out 

 little suckers. The branched mycelium gives off sporangia 

 and antheridia, exactly as in Peronospora. It is needless, 

 therefore, to dwell at length on this matter. When ripe, the 

 sporangia are strong warted. 



They fall down, doubtless, with the leaves upon the ground, 

 where they remain till a fitting season arrives for their develop- 

 ment. When sown artificially, they do not show any change 

 till after the lapse of some months. Those gathered in June 

 did not make any further progress till December. If leaves 

 containing sporangia, after being kept for some time, are 

 immersed in water, the surrounding tissues disappear, and the 

 sporangia are set at liberty. If placed at once in water, 

 moulds are often developed, and a species of Chytridiwm, so 

 that it becomes difficult to follow out the development. 



The epispore bursts irregularly, and the contents are 

 discharged still surrounded by the endospore, and exhibiting 

 one or two vacuoles (Fig. 10). The mass of protoplasm then 

 contracts towards the centre, is divided by delicate lines, as in 

 the acrospores of the potato mould, each containing a vacuole ; 

 these gradually become zoospores, which are soon discharged, 

 and closely resemble those produced from the conidia. 



We have, then, not only in Saprolegnice, but in undoubted 

 fungi, distinct antheridia. It is true that active spermatozoids 

 have in no case been observed in the antheridia, but the whole 

 mode of development is so exactly similar to what takes place 

 in Saprolegnice that we cannot doubt that they are really what 

 De Bary considers them ; and, if Pha?nogams do not produce 



