On the Besting -Spores of certain Fungi. 35 



night. When spores are sown on the leaf of some plant on 

 which they are not habitually parasites, they comport themselves 

 very much in the same manner as if they had been sown on 

 glass. 



In general, all parts of the mother plant above the surface 

 of the soil are indifferent. The potato murrain, however, attacks 

 the tubers, the germinating threads easily penetrating even 

 their thick cuticle. It is easy to conceive how the zoospores 

 can be washed down to them after heavy rains. In P. umbelli- 

 ferarum a stomatiferous surface is a necessity. 



The threads of the mycelium within the leaf, meanwhile, are 

 not inactive. They are generally more or less branched, some- 

 times forming at intervals tufts of thread, and very irregular in 

 outline. They produce on short lateral peduncles globose 

 bodies, which are destined ultimately to give rise to the resting- 

 spores. The metamorphosis of their protoplasm, which is either 

 grumous or filled with distinct definite globules, does not take 

 place, if De Bary's observations are correct, without the help 

 of antheridia, which are produced either by the side of the 

 sporangia, or on neighbouring laterals. They are obtuse, 

 shortly pedunculate, and either regular or irregular in form, 

 sub-globose, or more or less clavate. After they have come in 

 contact with the sporangia, which like themselves are at length 

 separated by a partition from the protoplasm of the mycelium, 

 they push out a little tube which penetrates their walls, making 

 its way towards the centre, till it comes in contact with the 

 young resting-spore (Fig- 8), very much in the way in which 

 the antheridia act in Saprolegnice. Various changes then take 

 place in the protoplasm; a central mass is formed, the outer 

 space being filled with large globular bodies exactly similar to 

 those which occur in Botrytis Tilletii and Polyactis ; the young 

 resting-spore soon acquires a membrane which either remains 

 even to the end, or becomes reticulated or variously sculptured 

 (Fig. 9). The surrounding cavity exhibits numerous vacuoles, 

 and the outer coat of the resting-spore is thickened, probably 

 at the expense of the protoplasm, which was not consumed in 

 the formation of the spore. If the spore is now macerated, the 

 outer reticulated coat vanishes entirely, leaving a perfectly even, 

 globose body, with two distinct membranes and the remains of 

 the fecundating tube still attached. Dr. Caspary, as appears from 

 his figures, evidently saw something of the antheridia, though 

 he does not appear to have suspected their nature. The most 

 perfect series of observations which De Bary has made are in 

 the chickweed mould, P. alsinearum, a species which has not 

 hitherto been gathered in Great Britain, but which in all pro- 

 bability could be found by any one who looked out for it. 



Unfortunately, the further development of these resting- 



