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THE AGPvTCI'LTUEAL XEWS. 



JiLv IS. 1914. 



FUNGUS NOTES. 



A NEW FUNGUS ON LIME LEAVES. 



Ill NuVL-mU-r liU'-'. Mr. jMseph .lom--. (■iiiat..r of the 

 liotaiiic Station, Dominica, forwarded to the C'ommi;>sioner of 

 Agriculture a number of lime leaves from the Senhou.-ie 

 IRstate bearing an abundance of example* of a small black 

 star-.shaped organism, which it wa.s thought might pos.sit>ly 

 Ije a fungus parasitic on the scale insects which were also 

 pi-esent on the leaves. The material was forwaided to Kew 

 Tmt proved to be unsuitable for diagnosis. Further supplies 

 liave been collected and sent on from time to time and these 

 have afforded material for the recognition of the systematic 

 position of the organism. A full description, with tigures. is 

 given by A. D. Cotton in an article in the Ke>r Bulletin, 

 Xo. '2. 1914 pp. .54-63, from which the following information 

 is extracted. 



The star-shaped bodies resembled a lichen siu-li as 

 CoUema in appearance, being gelatinous and swelling when 

 moistened, after the manner of species of that geuus. In 

 .".structure, however, they .showed a re.semblance to certain 

 niemliers of the red algae, being comjwsed of black monili- 

 iV)i]n filaments more or le.ss held together in mucilage, loosely 

 arranged in the centre and more compact tiiwards the peri- 

 jihery. The general structure was utterly unlike that of an 

 ordinary fungus, and from an alga the plant differed in the 

 fact that the filaments were apparently devoid of colouring 

 anatter. while from a lichen they were equally distinct thr.:>ugh 

 ihe absenie of gonidia — the algal cells characteristic of that 

 yroup. 



Additional supplies gave the necessary clue for identi- 

 fication. One of these samples provided the cc^nidia-like 

 sjxiries and the other abundance of a.sci and ascospores. The 

 presence of asci proved that the plant was not an alga, and 

 the absence of gonidia being confirmed its place had to be 

 •Siiught amongst the fungi. Here it was ultimately traced 

 !<■ the genus Atichia. 



The genus was founded Viy Flotow in 1S.5(I and for half 

 a century contained only one species: a small plant, supposed 

 t<j be a lichen, occurring on leaves of conifers in Southern 

 Europe. A .Javan species bearing ascospores, was discovered 

 "about 1900 on various hosts. In 1904 the same plant was 

 found in Poh^lesia and in 1906 another species was described 

 ■from Tahiti on vanilla. Two species are also recorded from 

 t'entral America and Chile respectively. 



sTRUCTUEE. The Atichia thallus is either an irregular 

 ^^ artlike or coralloid mass, or a flattened more or less stellately 

 branched body attached below by a small central point. It 

 is compo.sed of a .system of torulose almost articulated 

 filaments held together in mucilage. The filaments branch 

 irregularly and proliably anastomo.se: towards the periphery 

 the branching is dichotomous and the cells smaller and more 

 rlosely packed, so that a denser cortical layer results. These 

 li-rminal cells are not, however, laterally united, but remain 

 free. The thallus is colourless within, but externally it i,- 

 black owing largely to the peripheral cells being dark in colour. 



Three kinds of reproductive organs are knowii. a.scos- 

 jjiprc>, conidia-like cells which adhere in clusters (propagula). 

 and pyenidia. With regard to the asci, no definite 

 apothecia or perithecia are produced, but any part of the 

 tipper surface of the thallus may become fertile and develop 

 asci lietween the moniliform filaments in the cortical layer. 

 In some species the fertile portion is swollen in the form of 

 cushion-like pads, which in extreme cases mav almost amount 

 to discoid branches. The asci are oval and contain two- 

 celled hyaline or sub-hyaline spores. The conidia! type of 

 n-pi"duction is even more unusual than the ascigerous. The 



spores do not occur singly but in clusters, each of which 

 remains intact on liberation, and are producetl in great 

 quantities in cavities in the thallus. 



LIFE-HISTORY AND BI0L0(4V. With regard to the biology 

 of Atichia the following items may be recorded. Of the 

 early stages of the plant little is known, but the material 

 forwarded from Dominica supplied a .series of specinien.s- 

 showing all stages from the budding propagnluni to the 

 mature plant. Some of the leaves received were covered 

 with the mycelium of one of the Sooty Moulds (CapncKliaceae), 

 and on this the propagula had become entangled. In the 

 earliest stages their triquetrous outline is still visilile, but 

 owing to successive budding this is r-oon lost and the mass 

 liecomes spherical. When about .50 miirons in diameter these- 

 masses begin to assume, l>ut on a compressed scale, the 

 same type of structure as the mature plant, and show 

 differentiation into a soft, loosely arranged, interior, and 

 a denser cortical layer. These observations are impor- 

 tant in showing that Atichia is a tlistinct fungus, and not 

 a .stage in the life history of CajJiiodium or other genus as. 

 some WTiters have thought. Pr(K)f of this, however, was. 

 not needed, as Mangin and Patouillard's researches place the 

 question beyond doubt. The ray-like branches begin to 

 protrude as lateral outgrowths when the plant is quite young 

 (aliout 1 mm. in diameter), foin- or five rays first aijpearing,, 

 liut others follow so that the mature plant may be 7-10 rayed„ 

 The rajs, which are of unequal length, often remain simple, 

 but occasionally they fork or jiroduce short lateral Itranches. 

 A considerable variation in form is thus found, even in sjjeci-^ 

 mens occurring clo.se to each other: a point which should, 

 inculcate caution with regard to the use of external form ia 

 this genus. 



From what has been .said it will be t-een that there is no 

 necessary connexion l>etweenthel)ominicanfungus and the scale 

 Lfpidriaaphes heckii, though as a fact it is often found attached 

 to the latter. Some of the lime leaves forwarded were very 

 liadly attacked liy this pest, and the effect is seen in the 

 presence of sooty moulds and other fungi. The leaves of 

 Eacil:>orski's specimens are quite clean, and the fungus i.s. 

 sparsely scattered and attached directly to the leaf. The 

 same is also true of .some of the sjiecimens from I)oininica, 

 this being particularl.y the case in the second batch forwarded. 



The Dominica plant is descrilied as a new species under 

 the name Aiicliia dominicana, Cotton. 



Conditions Favourable to the Development 



of Mildew. Fi"Ui observatiiiii> in Fmiice it appear.> that 

 infection by mildew is due to (a) general causes; (b) secondary 

 causes depending on the nature and vitality of the vine, and 

 on its adaptation to local conditions, such as the comjwsitiou 

 and exposure of the soil: (c) accidental causes (such as 

 manure, tillage, drainage of the soil, etc.). 



As these general cau.ses are bound up with atnnwiiherifc 

 variations, mete<irological ol)servations are requiiti:! to provide- 

 warnings and tiiuelv information. Preventive measures can 

 always be successful in normal years when periods of infection 

 do not overlap each other, as happeneil this year at Eoussillon 

 (Pyrenees Orientales). 



For secondary and accidental causes, it is nece.ssary to 

 make researches into. the variations in the development of the 

 di.sea.se. For example, the variety Grand-noir will remain 

 free from disea.se though surivinindefl by the Carignan variety 

 badly infected: and the Carignan of Salanque (1), growing in 

 soil of nonnan humidity, will be protected from infection bj- 

 treatuient with cf)pper sulphate, owing to its adaptation to. 

 the local conditions. (Monthli/ Bulletin of A;/ricultural 

 I utelliijence and Plant Diseases, Octolier 1913.) 



