586 
NATURE 
[OcTOBER 9, 1902 
removed, and a body known as haematoporphyrin is then 
formed, which presents a most striking similarity to a derivative 
of chlorophyll which has been named phylloporphyrin. The 
two pigments are almost identical in their percentage composi- 
tion, the heematoporphyrin containing a little more oxygen than 
the other. Both seem to be derivatives of pyrrol. The most 
striking similarity between them is their absorption spectra, their 
‘ethereal solutions both showing nine bands of identical width 
and depth, those of heematoporphyrin being a little more towards 
the red end of the spectrum. Their solutions in alcohol and 
ether show the same colour and the same fluorescence. Though 
they differ in certain other respects, notably the facility with 
which they form crystals, it is impossible to deny that a close 
relationship seems probable. If this is established, we may by 
analogy perhaps learn something about the part played by iron 
in the action of the chloroplast, which so far has proved as 
obscure as the relation of the metal to the pigment. It is very 
suggestive to recall the resemblances between the two pigments, 
the one playing so prominent a part in animal, the other in 
vegetable life. Both are associated with a stroma of proteid, or 
possibly protoplasmic, nature, in which a solution of the pig- 
ment is retained, apparently after the fashion of a sponge. Both 
are concerned in metabolic processes in which gaseous inter- 
changes play a prominent part. Both are in some way depen- 
dent on the presence of iron for their individuality, even if iron 
is not actually present in the molecule of both. The iron being 
removed, the derivatives which are found are almost identical. 
Further researches may throw a light on this curious relation- 
ship, perhaps showing that chlorophyll may enter into a com- 
bination with carbon dioxide as heematin does with oxygen. Such 
a combination might well be the precursor of the decom- 
position of the carbon dioxide which has been already 
spoken of. 
We meet with another pigment in many plants the physio- 
logical significance of which has in recent years begun to 
attract some attention. This is the red colouring matter, 
anthocyan, apparently related to the tannins, which is developed 
especially in the young leaves of shade-loving plants when they 
become exposed to illumination exceeding the intensity which 
they normally encounter. The formation of this pigment is 
greatest in tropical plants, where it is found usually in the 
epidermis of the young leaves, though in some cases it extends 
to the mesophyll as well. The pigment seems in some way to 
be supplementary to chlorophyll, for its absorption spectrum 
shows that it allows all the rays useful in photosynthesis to pass 
through it. It is unlikely that it takes any share in photosyn- 
thesis. Several theories have been advanced to explain its 
presence ; it may be simply to protect the delicate cells from 
the destructive action of too intense light, or to avert the evil 
of overheating from the solar rays. It has been suggested that 
certain rays hinder the translocation of starch, and that the pig- 
ment shields the cells from the incidence of such rays. Again, 
the view has been advanced that the red colour is important in 
accelerating the development of diastase from its antecedent 
zymogen, which has been found to take place under the influence 
of the rays of a certain region of the spectrum. While all 
‘these views have been advanced, however, there is little 
positive information bearing upon either the formation or the 
function of the pigment. 
Very little progress has been made with the problem of the 
construction of proteid matter in the plant, which still confronts 
us. The question of its relation to the mechanism of photo- 
synthesis has received some attention without leading to any 
salisfactory conclusion. Winogradski’s success in cultivating 
the nitrate bacteria upon purely inorganic matter reveals an un- 
expected constructive power in some forms of vegetable proto- 
jplasm. The question of the energy made use of in proteid 
‘construction is in an equally unsatisfactory condition. Laurent, 
Marchal and Carpiaux have stated that the rays of the violet 
and ultra-violet region of the spectrum are absorbed and devoted 
principally to the construction of nitrogen compounds from the 
nitrates, or the compounds of ammonia, which are absorbed by 
the plant, while the intervention of the chlorophyll apparatus is 
unnecessary for this purpose. The experiments which they give 
in considerable detail upon this absorption carry much weight 
and appear conclusive. Unfortunately, other observers have 
failed to confirm them, so that at present the matter must be left 
open. 
Among the problems connected with the nutrition of the 
plant, the part played by alcohol has recently come into promin- 
NO. 1719, VOL. 66] 
ence. Alcohol was originally associated only with the lower 
fungi, and especially with the yeast plant. Biological problems 
of grave importance arose in connection with the Saccharomyces, 
apart from what seemed at first the larger question, viz. the 
nature of fermentation. A prolonged study of the latter 
phenomenon led Pasteur to the view that alcoholic fermentation 
is only the expression of the partial asphyxiation of the yeast, 
and its efforts to obtain oxygen by the decomposition of the 
sugar. It is hardly necessary here to remind you of the con- 
troversies that centred about the question of fermentation and 
the theories heldand abandoned as to its cause. The biological 
phenomena have, however, a claim now upon our attention in 
the light of some very remarkable researches that are calling 
for our attention and criticism to-day. Pasteur’s explanation 
of the behaviour of the yeast was, as we have seen, such as to 
connect it with the respiration of the plant. When oxyge. 
was withheld from active yeast, 60-80 parts of sugar disappeared 
for one part of yeast formed. When oxygen was present, not 
more than ten parts of sugar were decomposed for the same 
amount of yeast production. Undoubtedly the stimulus of 
asphyxiation materially stimulated the yeast metabolism. 
But certain observations did not agree with Pasteur’s explana- 
tion. An energetic fermentation takes place in the presence of 
oxygen, the plant multiplies extremely quickly, and its meta- 
holism appears very active. Schiitzenberger argued against 
Pasteur’s explanation with some force, emphasising these points 
of disagreement between his hypothesis and the facts, and 
claimed that the matter rather concerned nutrition than respira- 
tion. He based his view on experiments carried out to ascertain 
how respiration was affected under changed conditions. 
The results he obtained were briefly the following :— 
(1) Ina watery liquid without sugar, but containing oxygen 
in solution, the quantity of oxygen absorbed in unit time by a 
gramme of yeast is constant, whatever proportion of oxygen is 
present. 
(2) In a saccharine liquid containing albuminous matter as 
well as sugar, and with oxygen in solution, the same result 
is obtained, except that the quantity absorbed in unit time is 
greater. 
(3) In two digestions carried on side by side for some time, 
one being supplied continuously with oxygen and the other 
deprived of it, the former produced most alcohol. 
If the decomposition of the sugar had been the result of 
the respiratory activity of the yeast cells at the expense of the 
combined oxygen of the sugar, it would seem that fermentation 
should either not have taken place at all in the presence of free 
oxygen or that it should have been much less than in the other 
case, whereas the reverse is what is found. Hence Schiitzen- 
berger advocated the view that the sugar is alimentary and 
not respiratory. 
Certain facts mcre recently discovered support strongly the 
view that the nutrition of the yeast is the chief object of the 
process normally, though we cannot deny that when partial 
asphyxiation sets in, fermentation is resorted to by the plant in its 
difficulty, that it may obtain the energy normally supplied by the 
respiratory processes. The mode of decomposition of the sugar, 
however, the formation of alcohol and carbon dioxide, raises a 
question as to the exact form in which the nutritive material is 
supplied to the protoplasm. 
Of these more recent discoveries, the work of Devaux on the 
trunks of trees may be mentioned first, as it seems to point toa 
similar problem to the one connected with yeast. Devaux 
examined the composition of the air in the interior of woody 
stems growing under normal conditions, and found that the 
proportion of oxygen it contains often sinks as low as Io per 
cent., while in a few cases, in the most internal part of the 
tree, he found this gas to be entirely absent. The disappear- 
ance of oxygen becomes easier with every increase of tempera- 
ture. The partial asphyxiation is attended by the formation 
of alcohol in the struggling tissue, the spirit being detected by 
cutting up the branches of the trees and distilling them with a 
large excess of water. Devaux’s experiments were made upon 
a considerable variety of trees, among which may be noted 
Castanea vulgaris, Pyrus domestica, Alnus glutinosa, Ulmus 
campestris, Sambucus nigra and Ficus Carica. 
Similar results have been obtained by Mazé in some researches 
on seeds. When a number of these are submerged in water, 
micro-organisms being properly guarded against, they do not 
readily germinate, but their weight nevertheless somewhat rapidly 
diminishes. In some of Mazé's experiments with peas, he 
