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ON VARIEGATION IN PLANTS. 
1 
8 
the under face has none ; and by examining a section, he discovered that the parenchyma of the first is only 
achromatic or colourless. Again, the whitened part is thinner than the green part, and the small cells 
are destitute of the green granular substance (chlorophyll), which causes them to appear like white 
spots aggregately presenting a pale surface. M. Dutrochet held that they only derive their white tint 
from the air which is contained in the pneumatic cavities. We believe, also, that M. Dutrochet 
attributed to this ah- enclosed in the pneumatic cavities, all the forms of variegation. This view, however, 
though in part agreeing with the truth, is partly also opposed to the facts, as we shall show. It is 
true in this sense, that the variegation, as the natural white spots in Trifolium pratense, Arurn itali- 
cum, Pulmonaria officinalis, Begonia argyrostigma, &c, arc caused by the air, or a gas ; but it is not 
true in tliis sense, that it is pneumatic cavities (lacuna:) which enclose that air. Because a leaf is 
deprived of its white spots by submersion in water, and the extraction of its air by the pneumatic 
apparatus, M. Dutrochet concludes that that air exists in particular cavities. We are not of this opinion, 
because the microscopic study of the plants we have just instanced, has proved to us that that air some- 
times exists in the minute cells (cellulse), and sometimes in intercellular passages (meats). The cavi- 
ties in leaves are found, as is well known, especially in the inferior mcsophyllum (the inferior system 
of the diachyma), and it is not this inferior surface which presents these spots, and other markings in 
particular : on the contrary, the superior system of the diachyma, or the superior mcsophyllum in 
which the cellulse are prismatic, much compressed against one another, and filled with chlorophyll 
granules, is the surface especially on which the albine discoloration is almost always found: it is the non- 
lacuniferous portion. The phenomenon cannot, then, be considered according to M. Dutroehct's new. 
M. Treviranus offers better reasons for regarding variegation as a true malady produced from 
weakness (astheny) ; for plants which are variegated with white and yellow, grow more slowly, are 
more susceptible of cold, more readily acted on by frost, and a humid atmosphere ; they flower less 
profusely and less frequently than other plants, nor do they bear fruit so often or so plentifully. He 
observes, however, that there are species in which, notwithstanding their variegation, vegetation is 
vigorous, as in the Aucuba japonica. He also remarks that Pulmonaria officinalis grows in several 
localities without spots, and that Lamium maeulatum has its first leaves in spring spotted with white, 
while these spots disappear in summer. We believe that this phenomenon is of a different nature to 
that of variegation, and that it is not dependent on the same law. We have studied the spotting of 
leaves with some care, and we have seen, indeed, that tliis phenomenon is of quite a different kind to 
that of variegation, both in respect to the plants in which it is found, its anatomical cause, its position, 
its physiology, and other incidental circumstances. 
M. Treviranus observes, in respect to variegation, that nature alone can produce it, and that art 
cannot accomplish it. But he is contradicted in tins by M. Sagerct. Art preserves and propagates by 
budding, layering, or grafting what nature has produced. But it is difficult to determine the cause of 
Variegation in a tree growing in a forest, when the others surrounding it, growing in the same soil, the 
same air, and light, have none. To this reflection we may add, that those who think that variegation is 
always traceable to an initial etiolation, preserved and propagated afterwards to the neighbouring organs, 
cannot maintain their opinion with any advantage, for it is by no means rare to find light, or partly 
white leaves on the Rubus, growing where it is fully exposed to the sun. We know an instance near 
Liege, of an jEseulus Hippocastanum having a branch with variegated leaves: this branch grows exactly 
at the south side, and is not shaded at all by the other brandies, or the surrounding trees. Miller also 
cites a curious case : as is well known, there is a variety of Sempervivum arboreum with leaves mar- 
gined with white ; this was first obtained at Badminton, the seat of the Duke of Beaufort : a branch 
accidentally broken and detached from the species with green leaves, after having been B little dried, 
was planted, and on beginning to grow, it was found to have the new leaves variegated. Notwith- 
standing the authority of Miller, the fact mentioned seems to require confirmation. M. Treviranus 
regrets that the soil in which the shoot was planted has not been described : for there are some facts 
which indicate that here the soil exercises a very remarkable influence. Burgsdorf, cited b\ M. Trevira- 
nus, relates the follow ing :— Certain snails had [partially] eaten the cotyledons and the bark ol a 
Beech; but it survived this mutilation: the second year its leaves were variegated ■ the third year it 
was transplanted into a better soil, and there, by degrees, lost its variegated leaves. The Professor at 
Bonn made several observations, from which he affirms that trees with variegated haves, by being 
transplanted from a poor to a rich soil return to a uniform green ; so that, according to his view, 
th's phenomenon is connected with a particular debility in the vegetable juices, brought on bj a 
diminution of the absorption in the root, and which does not permit the parenchyma to assume the p 
green colour by the influence of solar light. 
Such are the facts and such is the theory cited amongst the best physiologists of the day, with the 
