402 



NATURE 



[August 24, 1893 



the calculation, he made use of the method employed by L. 

 Struve in his memoir on the determination of the movement of 

 the solar system, in order that the two results might be strictly 

 comparable. Prof. Bakhuyzen has also repeated the calcula- 

 tions, using stars in the same part of the heavens as the above, 

 but with prnj^er motions not exceeding o'oyf. The first 

 method gave, as the position of the apex, 



R.A. = 264°, Decl. = 30°. 

 The result obtained by the second calculation was — 



R.A. = 290°, Decl. = 24°. 

 The position found by L. Struve was— 



R.A. = 273°-3, Decl. = 27°-3. 



Prof. B.ikliuyzen is at present occupied in determining the 

 apex from stars of small proper motion in the Milky Way. 



The Origin of New Stars. — In the current number of 

 Die Nalttr Prof. G. Hoffmann surveys the various new stars 

 discovered since Tycho Brahe's Nova Cassiopeise, and the dif- 

 ferent theories advanced lo account for their appearance. He 

 n inclined to endorse the views of Prof Seeliger, according to 

 which the sudden biightness is produced by a heavenly body 

 • nlering a "cosmic cloud " consisting of sparsely distributed 

 matter. Prof. Hoffmann thinks that all new stars may be 

 legarded as essentially of the same type as the variables of long 

 period. 



THE MINUTE STRUCTURE OF PLANT 

 HYBRIDS} 



■P^R. MACFARLANE'S paper will not fail to impress bio- 

 '-^ logists by the suggestiveness of some of his speculations and 

 with the importance of his observations. Nor are his conclusions 

 limited to the plant hybrid?, which he discusse.", but they apply, 

 though with certain limitations, to all organisms resulting from 

 sexual reproduction. 



Of course, in the case of hybrids, the parental characters are 

 often very different, and can therefore be easily recognised in 

 the offspring, whence the examination of their characters, in- 

 cluding, of course, their minute anatomy, becomes important to 

 all who are interested in the problems of reproduction. For in 

 the case of fusion of reproductive cells of ihesame species, where 

 the parental characters differ often very slightly, it is difficult, 

 and at times impossible, to distinguish whether the characteristics 

 of the male or female parent predominate, or whether a com- 

 plete blending has taken place. Theoretically perhaps we should 

 expect this blending of characters, but our everyday experience 

 brings to our mind s-o many instances of almost unadulterated in- 

 heritance of paternal or maternal characteristics, that we are 

 somewhat prejudiced again- 1 a conclusicn to which Dr. Macfar- 

 lane's observations on hybrids lead him, and which ought equally 

 to apply to normal offspring. 



The study no doubt presents many difficulties, which are, it is 

 true, recognised by the author, but do not seem to him insuper- 

 able. First and foremost we have the variability of what are 

 usually termed true species ; and the author is careful to point 

 out that " for hybrid investigation one should be acquainted 

 whh the parent individuals and the conditions under which they 

 were grown, or try to choose an average specimen for study." 

 But in either case errors may creep in. For if one of the 

 parents has varied abnormally, though some of the offspring 

 will inherit such a variation, others may revert to the more 

 normal condition of their grandparents or great- grandparents. 

 If, on the other hand, we choose the average specimen, 

 we are entirely in the dark as to any special variation of the 

 parental form. Nothing short of selecting normal individuals 

 as parents and examining all or a large number of the hybrid 

 offspring would afford sufficient basis for such conclusions, as 

 the author deduces from his less complete obervations. 

 But Dr. Macfarlaned les not even state in each case whether his 

 observations are taken from the parents themselves, or only 

 from average specimens. 



The conditions of growth, too, enormously affect some of the 

 characters which the author has chosen for comparison. The 



?/'.■* Comparison of ihc Minute Slruclurc of Plant Hybrids, with that 

 oT their Paren's, and its Bearing on Biological Problems." By Prof. J. 

 Miiirhead Macfarlane. (Transactions ofthe Royal Society of ICd nbnrgh, 

 vol. xxwii. part i, no. 14.) 



NO. 1243, VOL. 48] 



character of leaves for instance, especially as regards their tran 

 piratory functions, can be conij/letely altered by the treatmci 

 of the young plant. If, therefore, the number of stomata pi 

 unit of surface are to be of any value for compariEon cf form' 

 both the parents and the offspring must be raised under simili 

 conditions. If this is not the case we .should expect the of 

 spring to resemble in this particular that parent which ws 

 grown under conditions most similar to itself. Nor does ili 

 author fail to find such a case, lledyihiutn ScuUerianum a| 

 proaches very nearly in the number of stomata on the lowt 

 surface the condition of one of its parents, //. (oronariiim ; lit 

 we are told nothing as to the condition under which thepareni 

 or offspring were reared, and the tendency to "sway towani 

 one parent " is explained by the assumption that it is " 

 morphological adaptation in the hybrid for physiological work 

 or in the truest sense a. case of physiological selection." 



Having thus briefly stated some of the difficulties bcsetlin 

 the problem, we may state that all his observations and measutt 

 raents, down to the size of the plastids and starch grains, leai 

 the author to the conclusion that plant hybrids, at least stn 

 hybrids, are, both in their minute structure and in their genets 

 life-phenomena, intermediate between their parents. 



Tills complete blending is, to say the lea.st, very exlia 

 ordinary, and we are tempted to question whether the auth 

 has investigated a sufficient number of individuals of eai 

 hybrid. Surely the variability of hybrids would be sufficient! 

 supply any investigator with numerous examples wh ch wer 

 not intermediate. The unanimity of the observations publishct 

 make it imperative that some further investigations should 1« 

 undertaken with regard to the variability of hybrids, a facto 

 to which sufficient prominence is not given in the preseii 

 paper. 



Darwin insists both in his "Forms of Flowers" and al,-< 

 in his "Cross and Self-fertilisation of Plants," upon tin 

 correspondence between the crossing of distinct species ai* 

 legitimate unions of dimorphic and trimorphic heterostjlet 

 plants. Yet from Dr. Macfarlane's paper we must conclude iba 

 in some respects at least there is no correspcndence. 



For Darwin states that though "the shape ofthe stigma an' 

 the length of pistil both vary, especially in the short styled fonn, 

 I have never met with any transitional states between the tin 

 forms in plants growing in a state of nature." Now the diStr 

 ence in these forms extends also to anatomical details, sachs: 

 the size of the pollen-grain and the size of the stigmatic bain 

 and yet the offspring will all resemble either one or ttie othei 

 parent, and thus differ radically from all the hybrids whicll Dr, 

 Macfarlane has examined, all of which rei resent forms inter 

 mediate between the two parents. Dr. Macfarlane has of co«is* 

 come across some exceptions, but we are not told whether the) 

 are merely individual variations approaching one or other of the 

 parents, such as we should expect to find, or whether in tht 

 production of the hybrid there was always a tendency to approxi- 

 mate the male or female form. Whichever he the case, the 

 author is ofthe opinion that the number previously asserted to 

 diverge towards one of the parents has been consideralJy over- 

 estimated. 



The author's contribution, however, to the investigation and 

 discussion of graft hybrids is extremely valuable, and we 

 cannot help wishing that he had found more similarity iotkt 

 characters ofgraft and seed hybrids. We feel convinced, thomgb 

 we should not like to impugn the evidence brought forward, that 

 the latter does not represent the average condition of the stric- 

 ture of plant hybrids, but that there must be more variation in 

 their characters than the author has found in the specimeni bt 

 was enabled to examine, especially more variation towards one 

 or other of the parent forms, though we should not expect it V: 

 be so pronounced as in the case of graft hybrids. F. E. W. 



COMPULSORY LAWS OF ERROR IN 

 DRA WING. 



Digest of the Phenomena, with Examples. 

 'T'HE object of the following paper is to present the facts in tht 

 briefest and, it is hoped, the plainest possible manner, foi 

 the purpose of calling attention to phenomena connected wil^ 

 the art of drawing, or depicting form in outline. It istoprovt, 

 that error made in such drawing comes under the dominion 

 natural law, or compulsion, and is not the result of individoa 

 misconception of truth. The phenomena are altogether distinc 



