Abstract
IN Mr. Cooke's article on this subject, it is stated that I have shown that there are at least four consecutive forms of reproductive cells in the bunt (Tilletia caries). I imagine that by a slip of the pen he must have substituted this for hop mildew; but, be this as it may, what I really did say at a time (1847) when the formation of secondary fruit was not ascertained in Ustilago, Puccinia, and allied parasites, was as follows, after describing the curious anastomosing threads which are produced on the germinating processes of the bunt spores:—“I was at first inclined to think that it had something to do with the reproduction of the bunt, and it is quite possible that in plants, as well as in the lower animals, there may be an alternation of generations. This is, however, merely thrown out as a hint which may be followed out by those who have fewer avocations than myself. Many anomalous appearances, amongst Algæ especially, seem to indicate something of the kind.”* This growth can only be regarded as an intermediate state, which is probably necessary for the propagation of the parasite, and the same must be said of other cases in which the anomalous form does not produce organisms similar to itself. In such cases as the hop and vine mildew, the Oidium forms may be propagated almost indefinitely with only an occasional production of another form, and this, perhaps, may safely be regarded as an alternation of generations, while mere conidiabearing forms can scarcely be so regarded. In such cases as that of the Uredos, which accompany or precede Puccinia, though both are fertile, we can scarcely recognise such an alternation; but if it is once established that a Puccinia produces an Æcidium, or an Æcidium a Puccinia, we should have a clear case. The usual argument about wheat being subject to mildew where there are no berberry plants, or Ræstelia where there are no savines, does not seem to me to be good. It appears quite clear that wheat mildew may be produced, either from the germination of U. rubigo vera, or from its own secondary spores, and that almost indefinitely, where there is no berberry; but this does not show that the spores of Puccinia, when sown on the berberry leaf, may not produce the Æcidium, or the spores of the Æcidium the mildew. I quite agree with Mr. Cooke, that the observations of Oersted and De Bary are not absolutely conclusive, though I may be inclined to give them more weight than he does. The observations should certainly be repeated; but, if the results should be the same, I should certainly feel inclined to accede to their views, indisposed as I always am either to jump hastily to conclusions myself, or to accede at once to the crude observations of others.
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BERKELEY, M. Alternation of Generations in Fungi. Nature 5, 122 (1871). https://doi.org/10.1038/005122a0
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DOI: https://doi.org/10.1038/005122a0
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