The Red Colouring of Arctic Plants

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<ul><li><p>The Red Colouring of Arctic Plants. 83MYCORHIZA AND ITS SIGNIFICANCE.</p><p>ln connection with Stahl's recent important work' on thesignificance of that intimate association of certain fungi with theroots of many plants known as "Mycorhiza" (now knownto be a phenomenon affecting probably considerably more than halfthe species of the higher plants), and his theory that Mycorhiza iscorrelated with a difficulty of obtaining nutritive salts, with feebletranspiration, and with poverty or absence of starch formation in theleaves, it is of great interest to note, as Dr. Wulff puints out (1) that aconsiderable number of arctic plants have Mycorhiza, (2) that of 16species collected and investigated by him all shew marked sugar-reaction,' and absence or poverty of starch, and (3) as has beenalready shown, arctic plants have a very feeble transpirationcurrent. Though the exact relations of these series of facts is notwholly clear, their causal connexion certainly seems indicated.</p><p>Thus the Mycorhiza-symbiosis would fall, at least so far as thenature of the soil in which the affected roots live is concerned, intotwo very distinct classes of cases; first, those in which the soil islargely composed of humus or leaf-mould, comparatively poor ininorganic salts, among which may be mentioned the beech and thehazel of our own woodlands ; and secondly those in which the soilis quite destitute of humus and while possibly rich in inorganicsalts cannot supply these freely to the plant owing to the lack of anadequate transpiration-current.</p><p>THE RED COLOURING OF ARCTIC PLANTS.</p><p>The extraordinary purity and brightness of the colours of manyAlpine flowers (and the same is true of Arctic ones) is well known.The vivid colouring often extends to the whole subaerial part of theplant, the leaves and stems shewing a deep red or purple whichoften masks the ordinary chlorophyll green. This is due to thepresence of soluble red, purple or blue pigments in the cell-sap ofvarious living cells ot the leaf and stem, very rarely [Eriophovumaiigiistifoliim vav. tniie) to colouration of cell-walls; to these pigmentsthe collective name Anthocyanin has been given. Dr. Wulff findsthat the presence of this pigment is an almost universal characteristic of Arctic plants. In a very interesting paper published three</p><p>' Dr. WulfF took precautions against coiifouuding siigai-reactiou with taimiii-reactiou.</p><p>' Der vSiuu der Mycorliizeiibilduug. Jalirb. f. wiss. Botaiiik,xxxiv., 1900.</p></li><li><p>84 Ecological Notes.years ago, Dr. Overtoil', of Zuricli, shewed that the development ofanthocyanin in leaves was nearly always conneeted with a deficiencyof starch und a corresponding increase of sugar (glucose); in otherwords, the anthocyanin, leaves are "sugar-leaves." Now, we havealready seen that of 16 species cf Arctic plants taken at random,(ill shewed marked sugar reaction. We therefore apparently havein the general occurrence of anthocyanin in Arctic plants anotherlink in the peculiar chain of their general economy. With regardto the actual position of anthocyanin in this chain. Pick- was ofopinion that the pigments in question facilitated the passage fromthe leaf of the products of assimilation, and in support of this viewWulff finds that the red cell-sap is sometimes confined to speciallayers of cells which may be carbohydrate-conducting in the petioleand stem. In the absence o.f mere e.xact knowledge of the chemicalprocesses by which this facilitation is supposed to take place, it mayhowever, be questioned whether the formation of the red or violetpigment is not primarily a direct result of the modified metabolicprocesses going on in the assimilating and conducting cells. Anaccumulation of pigment originally arising in this way may well beof use to the plant in enabling it to absorb more radiant energy,and thus to help out its rather feeble vital processes. This view ofits direct utility is held by Kerner' and is also endorsed by Wulff inhis present work.</p><p>RESEARCH IN BRITISH ECOLOGY.</p><p>Investigations of very difficult and fundamental problems inthe ecology of plants usually raise more questions than they answer,but this is a natural occurrence in research on subjects of whichour ignorance is so great, and only shews the necessity for activeand determined work in all directions. As the periphery of ourarea of knowledge is widened, its points of contact with the vastfields which are still obscure increase in number, and this isanecessaryfeature of all progress. Dr. WulfFs researches are an excellentexample of the kind of work that has to be done, not only on Arcticplants, but on those of plant-communities nearer home. Theecology of the British Isles is a strangely neglected field of research.On the whole, no doubt, our flora closely resembles that of North-</p><p>&lt; Beobachlungeu uud Versiiclie iiber das Auftieteu vou rotlieiiZellsaft bei Pflauzeu,Jabrb. f, wiss Bot., 1899.</p><p>' nedeutung des roten FarbstofFs bei deii PtiauerogamenBot, Ceiitralblatt, 1883.</p><p>' l'flauzenleben, i8g6, p. 379,</p></li></ul>