156 



NA TURE 



[June 12, 1890 



times when no alteration of external conditions is per- 

 ceptible, and they do not occur when such alterations are 

 very apparent. Or, again, they appear in one place under 

 one set of circumstances, and at another place, simul- 

 taneously, under a different state of affairs ; and although 

 all the plants growing together have been exposed to the 

 changed conditions of life, the sporting tendency shows 

 itself in one particular plant only, and in one particular 

 part of that plant, generally only in one bud. With all 

 respect, then, for those who hold these views — and one at 

 least of our most experienced and eminent plant-growers 

 has lately publicly advocated them — we venture to think 

 external causes, however adequate they may be in some 

 cases, are inoperative in such cases as we are considering. 

 A better explanation is that offered by Darwin, by 

 Naudin and others, according to which sports are due to 

 a dissociation of mixed elements, a reversion to the 

 character possessed by one or other of the ancestors of 

 the plant, perhaps one or two, perhaps an indefinite 

 number of generations ago. Let us recall for a moment 

 what a very composite thing a plant is, even such a one 

 as we call a simple plant. At first it is neutral and homo- 

 geneous, a mass of protoplasm, but the homogeneity of 

 protoplasm is a thing of the past. We do not believe in 

 it now. On the contrary, we believe in frameworks and 

 interstitial fluid, in granules and fibres, in some parts that 

 are alive, others that are dead ; some that are stable and 

 immutable, others that are mobile and changeable ; in 

 short, we have come to the conclusion that, physically 

 and mechanically, as it was previously known to be 

 chemically, protoplasm is very much " mixed." 



Again, another of our old beliefs has been dissipated. 

 Once we were taught that the cells of plants were closed 

 bags without apertures, and that, while the fluid passed 

 from cell to cell by osmosis, there wete no visible pores, 

 and no means of transmitting anything more solid than 

 cell-sap. The passage of protoplasm from cell to cell was 

 not then thought of as possible. But Mr. W^ alter Gardiner 

 has changed all that. He and others who have fol- 

 lowed in his steps have taught us how to see the pores 

 in the cell-walls, how to see the passage of protoplasm 

 through those pores from cell to cell, and how com- 

 placently to employ the phrase " continuity of proto- 

 plasm " in a manner that gives us, at present at least, 

 great satisfaction. These modern discoveries of the 

 composite nature of protoplasm, and of its passage, at 

 certain times and under certain conditions, from cell to 

 cell, seem to us to furnish a clue to the explanation of 

 some of these cases of sporting, as they do also in the 

 case of some of those curious cases in which the stock 

 seems to influence the scion, or the scion the stock, in 

 cases of grafting. 



Again, in the life-history of a plant there are several 

 stages. There is the neutral stage, when it is, at any 

 rate, so far as sex is concerned, an epicene. Then there 

 is the sperm stage, when our plant consists of a mass of 

 neutral matter, a particular portion of which is developed 

 into sperm-cells, or into what will ultimately produce 

 them. At another time the neutral cells of one portion of 

 the general plant-mass develop into germ or female cells, 

 or it may happen that both sperm and germ cells may be 

 developed at one and the same time, when the plant has, 

 of course, a three-fold constitution. 



All these modifications occur in the course of the life of 

 each individual plant. But each individual plant is, 

 necessarily, compounded of elements derived from its two 

 parents, so that, for illustration sake, if we may consider 

 the original stock to consist of three portions — neutral, 

 male, and female, respectively — it is obvious that in the 

 first generation there would be six component elements ; 

 in the second, twelve ; in the third, twenty-four, and so 

 on. Who can count the generations of plants? It is 

 enough for our purpose if we succeed in showing clearly 

 the composite nature of plants 



NO. 1076, VOL. 42] 



This being granted, it will not seem remarkable that 

 occasionally a partial separation takes place, just as a 

 scum may rise to the surface of some mixed fluid, or a 

 sediment fall to the bottom of another. This illustration 

 may, perhaps, serve to suggest the reason for the separa- 

 tion of mixed elements in plants ; but that is too specula- 

 tive a matter for us to enter upon here. It will be better 

 for our present purpose to note one or two examples of 

 dissociation of mixed characters wherein both the fact 

 and its explanation are clear. One of the most interesting 

 is that narrated by Mr. Noble, the originator of the white 

 form of Jackman's Clematis. Noble's Clematis, as we 

 may here shortly call it, is the result of a cross between 

 Jackman's Clematis and C. patens. Soon after this 

 Clematis was sent out, some dissatisfaction arose because, 

 instead of producing flowers of good form and purity of 

 colouring, more or less misshapen blooms of an un- 

 attractive appearance were formed. The matter was 

 mysterious. The raiser was blamed by those who did 

 not know that he is a highly competent man in his 

 business, and one whose integrity is beyond question. 

 The plant was condemned. Fortunately, however, the 

 edict was not carried out in its entirety — some specimens 

 were left. These were watched, and in due time afforded 

 the explanation of the mystery. Jackman's Clematis 

 flowers in the autumn on shoots formed during the spring 

 and summer — on the new wood, as gardeners say, just as 

 happens with a Rose. Clematis patens flowers in spring 

 on shoots that were formed during the previous summer, on 

 the " old wood," in gardening phrase. Now, when Noble's 

 Clematis came to be scrutinized, it was found that it pro- 

 duced two kinds of flowers. Those which expand in spring 

 are solitary, semi-double, never white, but bluish-gray, 

 like those of C. patens. Those which unfold in autumn 

 are produced in pairs and are single, like those of C. 

 yacknianni, but white. In the spring no flowers of the 

 Jackman type are ever seen, and when the old wood is 

 cut away, and only new wood thus suftered to produce 

 flowers, no blooms of the patens character are seen, but 

 only those of the Jackman type. 



Another very interesting case of unmixing, or, if it be 

 preferred, of partial mixture, is afforded by Neubert's 

 Berberis. This is a hybrid between the evergreen pinnate- 

 leaved Mahonia and the deciduous simple-leaved Berberis 

 vulgaris, and it bears leaves some of which are inter- 

 mediate in appearance, while others are like those of one 

 or of the other of its parents. 



The two illustrations above given are instances of the 

 results of cross-fertilization, in which the whole process 

 has, so to speak, taken place under our own eyes. But 

 for how many centuries has the Chrysanthemum, we will 

 say, been crossed and recrossed and crossed again ? 

 This process of crossing seems destined to come to an 

 end, because the flowers, after a time, become sterile, 

 owing to the fact that the stamens and pistils, one or 

 both, are imperfectly or not at all developed. Seedling 

 variations in such cases must become more and more rare 

 as the process of sterilization becomes more and more 

 marked. If new seedlings are desired, raisers will have 

 to go back to less highly modified flowers — to flowers, 

 that is, which are more nearly in their original con- 

 dition. But although the production of varieties in the 

 Chrysanthemum by fertilization is thus limited, the 

 development of sports by bud-variation may, and prob- 

 ably will, still go on, to the delight of the grower and the 

 interest of the student. It must, however, be said that 

 at least in the case of the Chrysanthemum the change 

 is sometimes very slight, depending solely on the 

 presence of colouring matter in some cases and on its 

 absence in others. The form of the flower and of the 

 ' foliage in many of these Chrysanthemum sports is in no 

 ! wise different from that of the parent plant. This is only an 

 I illustration of the fact that all degrees of combination or of 

 1 dissociation, as the case may be, may be expected to occur. 



