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forming minute separate bodies in the acrospore ; these are 

 zoospores, resembling small infusoria. When the acrospore is 

 fully ripe it bursts with some force and scatters the contained 

 minute bodies to some distance; thus liberated they move 

 about very freely by means of their cilia : and then, eventually 

 finding a resting-place favourable to their development, their 

 cilia drop off, and after a little rest, strange as it may appear, 

 a transparent tube or mucedinous thread proceeds from them, 

 and entering by the stomata, they draw their sustenance from 

 the plant on which they rest, producing more mycelium, and 

 therefrom eventually fertile stems with acrospores containing 

 another generation of zoospores. 



The branchlets of the fertile stems also produce conidia or 

 secondary spores, sometimes called dust spores ; it is assumed 

 that both the acrospores and the conidia are assexual. De 

 Bary states that one square line will contain 19,620 zoospores, 

 under favourable conditions sufficient to destroy an immense 

 number of potato plants ; they are thus fraught with much 

 importance to the producers of such an extensively used 

 article of food as the potato. 



The second method of propagation is by resting spores, and 

 we find these in and on the mycelium in the midst of the leaf 

 and in the heart of the tuber, they are the production of oginia 

 with antheridia. The antheridia are very small semi-opaque 

 or very faint grey brown bodies attached to the mycelium by 

 fine threads, these are attracted too and are absorbed by the 

 oginia or ovarian sacs which afterwards produce resting spores. 

 The oginia are larger than the antheridia and are of a pale 

 grey brown colour before fertilization, but they become dark 

 brown when the spores are ripe. 



'When Mr. W. Gr. Smith first stated that the resting spores 

 under consideration produced P. mfestans, some eminent 

 Continental scientists were sceptical on that point; and it 

 led to some interesting experiments being made. Some of the 

 turbid fluid which flowed from an infected tuber, and which 

 was almost one mass of mycelium, antheridia, and oginia, was 

 set aside and carefully protected for examination. For three 

 or four days the parts of the fungus floated and grew, the 

 antheridia and oginia conjugated and were present in 

 abundance at the bottom of the liquid, and a photograph of 

 these minute bodies in conjugation was secured. The fertilized 

 oginia, the future resting spores, were then preserved in sealed 

 bottles and placed aside until the month of April in the 

 following year. At that time some of the spores were taken 

 out of the bottle and placed in pure water, some in potato 

 liquor, some in saccharine fluid, some in nitrogen, some 

 between glasses constantly moist, some on broken tiles, and 

 some on the potato leaf as it was growing. These were under 



