Dec. 7, 1 87 1 J 



NATURE 



109 



Oersted contends that if these secondary unilocular spores 

 are sown upon young plants of the Sorbus auciiparia, 

 they will germinate, and that the ends of the germinating 

 filaments penetrating the tissues of the leaf of the sorb will 

 in turn produce the spermagonia and peridia of Ra-stclia 

 coTiiuta. This is very similar to the deductions of Prof, 

 de Bary that the spores of the .■Ecidiuin which flourishes 

 on the berberry may be employed to inoculate young 

 plants of wheat, and will produce as a result the wheat- 

 milde.v P:icc!iiiagraiii!i!!s), which he contends is another 

 generation of the berberry fungus completed upon a 

 different host. {See Nature, vol. ii. p. 318 ) 



Such experiments as those of Professors Oersted and 

 De Bary must always prove unsatisfactory unless per- 

 formed with extraordinary care, and until confirmed by 

 other observers. One or two strong presumptions can 

 always be urged against them, and require to be boldly 

 faced. Wheat is very subject to the attacks of mildew 

 {Piicriia'a), and the results claimed for certain experiments 

 are that they have produced by inoculation with other 

 spores the common Piiccinia upon wheat plants, to which 

 the wheat is particularly addicted all the world over. 

 Admitting that the A^ciditim spores sown on the leaves 

 of young wheat plants germinate, and that the germinating 

 filaments enter the tissues of the leaf, are we therefore 

 justified in affirming, or admitting that the inoculating 

 spores produce the Pitcchua which ultimately exhibits 

 itself.'' Is it not more feasible to believe that the germi- 

 nation of the foreign spores have only served to stimulate 

 the latent germs of the Piiccinta already present in the 

 tissues of the wheat plant ? What guarantee is afforded 

 by those who have already experimented, that the wheat 

 plants experimented upon would not ultimately, without 

 inoculation, have developed precisely the same parasite as 

 that supposed to have been produced by inoculation .' 

 Assuming also that the experiment was pursued in the 

 opposite direction, and that the spores of the wheat mildew 

 were sown upon young plants of the berberry, if the 

 A^cidiiiiii should soon afterwards appear on the leaves, it 

 is easy enough to jump to the conclusion that they were 

 produced by inoculation, but assumption is insufficient 

 since the berberry is very subject, year after year, to bear 

 on some of its leaves the peridia of the ^-Ecidiiim. What 

 evidence could be given that the .'Ecidimn would never 

 have appeared but for the inoculation .' It is manifest that 

 no amount of care in cultivation under bell glasses or other 

 exclusion from foreign influences is sufficient against a 

 contingency which dates back to the seed of the nurse- 

 plant. 



If the sowing of the spores of JEcidium upon the leaves 

 of wheat resulted in the production of an ALcidrntit iden- 

 tical with it, or if the inoculation of berberry with wheat 

 mildew was succeeded by the development of a Piiccinia 

 of a very similar character, it would not be so difficult to 

 believe in both cases that the resulting forms might have 

 been caused by inoculation. When the fungi assumed to 

 be produced by inoculation are those to which the nurse- 

 plants are particularly and specially subject, the evidence 

 should be very strong before it is affirmed that a very 

 natural phenomenon had an unnatural * cause. 



The evolution of Raste/ia on the leaves of the " moun- 

 tain ash " by inoculation with Podisoma spores is quite 

 analogous to the berberry and wheat fungi. It is common 

 enough to find the Podisoma on junipers, and the Ra'stclia 

 on " mountain ash," and the presumption would be, if 

 young plants of " mountain ash " were covered up ever so 

 carefully with bell glasses, notwithstanding that the leaves 

 had been sprinkled with the spores of a dozen other 

 species of fungi, if Ra-slclia made its appearance, that it 

 bore no relation whatever to any of the foreign spores 

 w-hich had been sown upon it, but would have been there 



"* The term " unnatural " 

 cause is one of which we h£ 

 ordinary course of nature. 



nployed here in the sense that the presumed 

 10 e-vperience, and which is contrar>' to the 



independent of inoculation, or bell glasses, or a dozen like 

 contingencies. 



In both cases to which allusion has been made above, 

 there is need of the strongest evidence to show that the 

 ultimate parasite would not have made its appearance 

 but for the inoculation, or that the whole chain was com- 

 pleted which connected the inoculating spore with the 

 parasite produced. It would be folly to contend against 

 facts for the sake of theory, and absurd to combat con- 

 clusions fairly deduced from ascertained facts ; bi:t in 

 this instauji we arc bound to c j.ilcnJ, in honesty to our 

 convictions, that in neither case has Oersted or De Bary 

 shown to our satisfaction that they were justified in de- 

 claring for an alternation of generations of fungi in which 

 the stages were passed on different nurse-plants. When 

 the facts are confirmed and established will be time 

 enough to inquire whether both stages are essential the 

 one to the other, and, if so, hoAr it is that mildewed wheat 

 in such great profusion can be found in districts where 

 berberry bushes are unknown, or why the Rivstelia on the 

 leaves of pear trees should be so common in counties 

 where scarcely a savin can bo found. 



I have been led to these observations partly because 

 some writers have accepted the conclusions at once as if 

 they were incontrovertible facts, and partly because I 

 have personally been charged with ignoring (by silence, it 

 is presumed) the results of De Bary and Oersted's experi- 

 ments, whereas I only claim the privilege of doubting 

 where I would not dare to deny. 



M. C. Cooke 



THE SCIENCE AND ART DEPARTMENT 



'HPHE following important Minute on the subject of 

 -'- Science instruction has recently been issued by the 

 Committee of the Privy Council on Education : — 



It appears desirable that the instruction of students in 

 Science, after they have completed the course of the 

 ordinary elementary school, should be carried on more 

 methodically than is at present the case, and that they 

 should not attempt to grapple with the more advanced 

 forms of Science until they have received sound and prac- 

 tical instruction in those subjects which constitute the 

 groundwork of all the physical sciences. 



To this end the course of instruction specified below 

 has been prepared as adapted both to secondary day 

 schools and to night classes. 



It will depend on circumstances, especially if the 

 student can only attend night classes, how many subjects 

 he can take up in one year. It must therefore be under- 

 stood that the course should not only comprise the sub- 

 jects named below, but also that they should be taken in 

 the order in which they are stated. 



The terminology used is that of the Science and Art 

 Directories. The syllabus of subjects there given states 

 precisely what is included under each head. And it is 

 assumed that before commencing the following course, the 

 student will have been made acquainted, in the elementary 

 school, with the elements of arithmetic, and the primary 

 conceptions of physical science. 



Course of Instruction. — First Year. — Mathematics 

 (Subject v.. First Stage) ; Freehand Drawing (2nd Grade 

 Art) ; Practical Plane Geometry (2nd Grade Art) ; Ele- 

 mentary Mechanics, including the physical properties of 

 liquids and gases (Subject VI., First Stage) ; Physics : 

 Acoustics, Light and Heat (Subject VIII., First Stage). 

 Second Year. — Chemistry, Inorganic ^Subject X., First 

 Stage), with practical work ; Physics : Magnetism and 

 Electricity, frictional and voltaic (Subject IX., First 

 Stage) ; Mathematics (Second Stage and, if possible, 

 Fourth Stage, Subject V.) ; Practical Geometrj'. Plane 

 and SoUd (Suljject I., First Stage) ; Animal Physiology, 

 if possible (Subject XIV., First Stage). The student 



