Vol. IX. No. 211. 



THE AGRICULTURAL NEWS. 



175 



shape of the spores: whether they are borne singly, in 

 chains, or in heads; if they are one- or more-celled; and 

 similar characters. Bamnlaria areoln, causing areolate 

 mildew of cotton, is included in this family, as well as 

 different genera causing mildews of grapes, roses and many 

 other plants. Many of them have been shown to be stages 

 in the life-history of ditterent species of the Ascomycetes. 



In the Dematiaceae, the hyphae, or conidia, or both, are 

 brown or blackish. The genera are separated by characters 

 similar to those dividing the genera of the .Mucedinaceae. The 

 group includes the genus Cladosporiuiu, one species of which, 

 C. e/fi/ans, causes a well-known disease of the orange; and the 

 genus C'errospora, of which V. i/os-ti/jii iia causes leaf spot of 

 cotton. This fungus is really a stage in the life-history of 

 Sphaerella i/ossi/jn'/ia, an Ascomycete. Other species are 

 responsible for various leaf spots on cott'ee, ground nuts, and 

 sugarcane. The pineapple disease fungus of sugar-cane, 

 Thiehii'idpsis tthaceticns, is also a member of this family. 



In the Stilbaceae, the hyphae are woven together to form 

 a more or less erect, cylindrical stroma, from which conidio- 

 phores are produced, either terminally or all over. The 

 con'dia are one- or more-celled, and, together with the stroma, 

 are frequently coloured. To this family belongs the genus 

 Isaria, whose species are frequently i)arasitic on insects: 

 larvae, pupae and the fully developed insects being attacked: 

 many of the species are stages in the life-history of members 

 of the ascomycetous genus Corih/aps. (See Ayiicnlturai 

 Neu'-t, Vol. I.X, p. 30.) Another genus in this family is that 

 of Stilliclld, of which StilMI'i tfiii'i In has rt^cently been shown 

 by Mas.see to be a stage in the life-history of the A.scomycete 

 Sphaerostil/je Jiaviduin. The conidial stage has long been 

 known as causing the important cott'ue disea.se of the New 

 World. (AfiririiHural News, Vol. VIII, pp. 39.5 and 411.) 



In the Tuberculariaceae, the hyphae and conidiophores 

 form a conidial patch or sporodin-hiuin, which Ls usually 

 disc-shaped or etiused, and freciuently coloured. The conidia 

 may be uni- or multicellular. The genus Fusariiim is 

 contained in this family. Fig. .'52 shows two stages in the 

 life-history of Fus-trinm I yropcrsicl, which causes sleeping 

 disease of tomatos. Many of its species are stages in 

 the life-history of diti'erent species of Xeabria and allied 

 genera. Ths genus Mirrocera is also included here. One 

 species, formerly known as Mirroceni voccojihila, is common in 

 these islands as the usual form of the reil headed fungus of 

 scale insects (S/Jiaerostilhe roi-rojiliila), which is closelj' allied 

 to the nectrias. 



These, then, are the main divisions of the fungi. In order 

 to present a more concise idea of their relationships, a tabular 

 diagram will be given in the ne.xt number of the Aiji-iciilttiral 

 News, which is intended to summarize as simply as possible 

 the main points in the information included in this series of 

 articles. 



The Black Fungus in Montserrat.— Some crotou 

 plants have been received recently from Mr. W. Ilobson, 

 Curator of the Montserrat Botanic Station, which showed the 

 presence of a bluck fungus resembling, as he pointed out, 

 Jfyrian</ium Duriaei, the parasitic fungus of the snow scale 

 {Chionaxpis citri), a well-known parasite of the lime. Further 

 examination revealed the presence on the plants of an allied 

 insect, (_' liiiniaspis hidains, on which the fungus was parasitic. 

 This is of interest, since the scale is one of the burrowing 

 species, and the occurrence of the fungus upon it has not been 

 recorded previously in the West Indies. The fungus was, 

 however, found on the insect by Parkin, in Ceylon, as is 

 recorded in the Aimah of the Royal Jiotunit: (hardens, Pera- 

 deniya, Ceylon, Vol. Ill, Part I, p. 32. 



THE EFFECT OF ELECTRICAL DIS- 

 CHARGES ON GROWING PLANTS. 



An account of work which has been undertaken by the 

 Department of Economic Biology, Bristol University, for the 

 purpose of ascertaining what effect there is, if any, on the 

 growth of plants, when they are subjected to a silent electric 

 discharge, is given in the Journal of the Board of At/ri- 

 cxdture, April 1910. In the trials, it is assumed that benefit 

 accrues to a plant when a small electric current is passed 

 through it, so that its yield is increased, and the time which 

 it takes to obtain maturity is lessened. It is probable that 

 this really takes jilace through an increase in the slight 

 electric current which is always passing through the plant 

 owing tci the fact that the atmosphere above it is at a higher 

 potential than the plant itself. 



At present this is only an a.ssumption, and much more 

 work will have to be done before decided opinions on the 

 subject can be gained. The present position of the contro- 

 versy may be summed up in the words of the article as 

 follows : It is sufficient to say that electric currents are report- 

 ed by many observers to have an optimal value for the plant they 

 are traversing, an oi)timum which jirobably is variable for 

 different plants and for the same plant at different times; and 

 that up to this optimum, increase in the strength of the 

 currents leads to increased growths, more rapid germination, 

 increased storage of food, and so on, but beyond this 

 strength, the current rather inhibits vital activities and tends 

 to lower the resultant yield from the [ilant. 



The experiments seem to indicate that more importance 

 should be attached than is usually the case to the effect of the 

 current in accelerating the development of the crop. Such 

 an acceleration would often have the effect of bringing it about 

 that the crop is gathered under better circumstances than if 

 it had had to remain until the usual time of harvest. There 

 is the additional consideration that the existence of such 

 acceleration denotes that the vitality of the plant has been 

 raised, and this would have an effect in increasing its power 

 to resist disea.se; actual indications of such increase have been 

 obtained, but they are not conclusive, owing to the conditions 

 under which the experiment was conducted. Some investi- 

 gators have stated that they have noticed increased chemical 

 activity in the electrified [ilants, especially Pollacci, who has 

 obtained indications that leaves can manufacture carbohyd- 

 rates, using the carl.)on dioxide in the air, when they are 

 traver.sed by an electric current, even when there is not 

 sufficient light for the purpose. 



In interpreting the results of work of this kind, regard 

 must be had not only to the effect of the current on the plant 

 itself, but also, on the contents of the atmosphere and the soil. 

 The presence of the electric discharges causes a combination 

 of the oxygen and nitrogen in the air, so that it is possible 

 that ultimately, there is a very small continuous addition of 

 nitrates to the .soil in which the plants are growing. It is 

 also very likely that the current will have its effect on the soil 

 bacteria, and thus upon the interchange that is taking place 

 between the soil and the roots of the plant; the knowledge, 

 however, of this part of the subject is too small for any definite 

 conclusion to be given. 



The results presented at the end of the paper would 

 appear, in a general way, to indicate that there is a practical 

 increase in the yields of crops when the growing plants are 

 submitted continuously to the in'fiuence of a high-tension, 

 silent, electric discharee. 



