NATURE 



\Dec. 14, 1871 



is to be hoped that some English lithographic printer will 

 see the American triumph in this particular, and will 

 forthwith mend his ways. P- M. D. 



LETTERS TO THE EDITOR 



r The Editor does not hold himself responsible for opinions expressed 

 by his eorrespondents. No notice is taken of anonymous 

 communications. ] 



Alternation of Generations in Fungi 

 In Mr. Cooke's article on this subject, it is stated that I have 

 shown that there are at least four consecutive forms of reproduc- 

 tive cells in the bunt ( Tilldia 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 anastomosini; threads which are produced on the ger- 

 minating processes of the bunt spores : — "I was at first inclined 

 to think that it had something to do with the reproduction of the 

 hunt, 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 du'own out as a hint which may be followed 

 out by those who have fewer avocations than myself Many 

 anomalous appearances, amongst Alga; especially, seem to indi- 

 cate something of the kind." * This growth can only be regarded 

 as an intermediate state, which is probably necessary for the pro- 

 pagation of the parasite, and the same must be said of other cases 

 in which the anomalous form docs not produce organisms similar 

 to itself In such cases as the hop and vine mildew, the Oidium 

 forms may be propa-jated almost indefinitely with only an occa- 

 sional production of another form, and this, perhaps, may safely 

 be r<r''arded as an alternation of generations, while mere conidia- 

 bearing 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 yEcidium, 

 or an ^'Ecioium a Puccinia, we should have a clear case. The 

 usual argument about wheat being subject to mildew where there 

 are no berberry plants, or Rcestelia wfiere there are no saviups, 

 does not seem to me to be good. It appears quite clear that 

 ■wheat mildew may be produced, either from the germination of 

 U. rubi'TQ vera, or from its own secondary spores, and that 

 almost tndefinitely, 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 /Ecidium, or the spores of the /Ecidium 

 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 observa- 

 tions of others. M. J. Berkeley 



Whether Mr. Cooke has sufficiently appreciated the labours of 

 De Bary and Oersted, in his article published in your columns of 

 last week under the above title, I leave for others to determine. 

 1 wish now merely to call attention to one sentence in his article, 

 as follows : — " It is manifest that no amount of care in cultiva- 

 tion, under bell glasses or other exclusion from foreign influences, 

 is sufficient against a contingency -uihich dates back to the seed of 

 the niirseplant." Does Mr. Cooke mean that the spores of the 

 fun"i themselves deposited in the seed of the nurse-plant are 

 carried up, so to speak, in the process of growth, mto tlie leaves, 

 where they germinate ; or that the liability to produce parasitic 

 fun^i is communicated from the seed to the mature plant by some 

 process which combines the Pangenesis of Darwin with the spon- 

 taneous generation of Bastian ? I see no other explanation of 

 the sentence than one or other of these alternatives. 



Mycelium 



Leibnitz and the Calculus 



Prof. Tait need not wonder if an attack that i^ "totally 



unexpected " should seem "appallingly sudden." In the absence 



of a statute of limitations restricting to two years and a half 



* " Journal of Horticultural Society of London," vol. ii. p. 111. 



the right to take up a gage, there can be no reason why an attack 

 should not be made, save its personal bearings ; and the circum- 

 stances of the challenge might be cited in bar of any exception 

 taken on that ground. I thank the Professor for his explanations. 

 I could not have guessed that under cover of his challenge to 

 produce a metaphysician who was also a mathematician, lurked 

 the assumptions, that every mathematician was a inetaphysician, 

 and that every metaphysician was either a mathematician or (in 

 the old sense) a physician. Well, he has a perfect right, for his 

 own private convenience or pleasure, to identify two names which 

 he had from the th-st asserted to be eternally distinct. Accepting 

 his classification, then, for the sake of argument — certainly not 

 for fruitless controversy — to wit, that everyone is either a mathe- 

 matician or a non-mathematician, and that every true metaphy- 

 sician must be either mathematician or physician (Faraday did 

 not hate the term "physicist " worse thin I do) we are confronted 

 with some surprising results. Leibnitz, the author of the Mona- 

 dologie and the Theodicee, works that are known to contain the 

 germs of the Kritik der reinen Vernuiift, was a spurious meta- 

 physician. Why, in the name of common sense? "Because," 

 says Prof Tait, " he was a non-mathematician ; there is no 

 medium, you know ; he must have been either a non-mathema- 

 tician or a mathematician, and a mathematician he was not." 

 What! Leibnitz not a mathematician ? " Not a bit of it," says 

 Prof Tait ; " for he was, I fear, simply a thief as regards 

 mathematics, and in physics he did not allow the truth of New- 

 ton's discoveries." I do not object to the Professor colling a 

 spade a spade ; but I assure him that this charge is made just 

 twenty years too late. It is exactly that time since tlie last 

 vestige of presumption against the fair fame of the great German 

 was obliterated. If Prof Tait does not understand me, or, 

 understanding me, disputes the unqualified truth of my statement, 

 I promise to be more explicit in a future letter. But I incline 

 to think the question is not susceptible of proof until the 

 Council of the Royal Society, who so grossly disgraced them- 

 selves in 1712, shall do the simple act of justice and reparation 

 required of them, viz., publish the letters and papers relating 

 to this controversy, which since that date have slumbered in the 

 secret archives. I advise Prof. Tait to utilise the meantime by 

 reconsidering some of his utterances on the Principia, lib. 

 ii. lem. 2. 



It appears, too, that Descartes, notwithstanding his physics, 

 which are very sad, was a mathematician, and therefore a true 

 metaphysician, and this, I suppose, despite the spurious meta- 

 physics of his Discours and his Meditations. By the way, when 

 Prof Tait parenthetically and admiratively corrects me for calling 

 him Cartes, he surely overlooked the fact th.-it Cartes is his English 

 name, the name by which he was known to the readers of Dr. 

 Samuel Clarke, &c., and is therefore preferable to the dog-latin 

 alternative. 



Such, then are some of the surprising results of adopting Pro 

 Tait's classification of mathematicians and metaphysicians. But 

 he objects to my classification of the former, that the greatest 

 mathematicians of our own day — among which Prof Tait will 

 allow me to count himself — would fall into my second class, 

 since they are not inventors of a calculus, and ^et they are not 

 mere experts. Among ihe names he adduces are Cayley and 

 .Sylvester, the co-inveniors of a new calculus, viz., that which 

 has been so fertile in its application to Linear Transformations ; I 

 mean, of course, the Higher Algebra. Accordingly, both would, 

 of course, fall into my first class ; and I will adcl, that I should 

 assuredly think that " something is rotten in the state of Den- 

 mark" if I found the true mathematical ?roi))T)fs had ever con- 

 tented himself with the improvement and application of other 

 men's pro luctions. C. M. Ingleby 



Highgate, Dec. 4 



The Science and Art Department 

 I HAVE been expecting, but in vain, to see Mr. Uhlgren's 

 reply to the request made to him a few weeks since, to produce 

 the Department's letter of which he spoke, and in which it was 

 stated that therumouied reduction of the number of certificates 

 awarded had actually taken place through the examination papers 

 having beeti retu ned for revision. I quite agree with your 

 correspondent who challenged its production, that such a docu- 

 ment (.)ught to be made widely kijovvn if it exists ; whereas if 

 Mr. Uhlgren's statement is f uurled on any misapprehension, 

 it ought to be corrected without delay. 



If such a statement were unlounded, such complaints as those 

 Mr. U. made are, I think, more likely to damage the cause of 



