142 



THE AGRICULTURAL NEWS 



April 30, 1910. 



FUNGUS NOTES. 



THE CHIEF 



OF FUNGI. 



GROUPS 



Pai;t ^■. 

 The Ai^ioMYCKTKs (cnminued). In the last number of 

 tlie Affrkuhuyal .\\-(r» the characters of the chief subdivisions 

 of this large giouii of fungi were considered, mainly from the 

 point of view of tlie ascus fructifications. It now remains to 

 make a few general remarks about the other spore forms 

 belonging to the group. These arc very numerous and varied, 

 and can only be discussed very shortly here: a more elaborate 

 account of them will be given when con- 

 sidering the Fungi ImperfecCi, to wh'ch 

 many of them wore at one time thought 

 to belong. The conidial spore forms may 

 roughly be divided into three groups. 

 Firstly, there are those in which the 

 spores are borne freely exposed to the air, 

 the conidiophores arising directly from the 

 hyphae of the vegetative mycelium, as 

 in the mildews and moulds. Secondly, 

 forms in which the conidiophores arise as 

 terminal or lateral branches of hyphae, 

 woven together to form a more or less 

 definite fructification, as, for e.xample, 

 the red heads of SphaerostiUje cocroj'hild 

 on scale insects, and the Fusariuiii stage 

 of the cacao canker fungi. Thirdly, forms 

 in which the conidiophores and conidia 

 are contained in closed fructifications, often 

 opening by a pore, kni:)wn as pi/cnidia, 

 and closely resembling the perithecia of 

 the Pyrenomycetes. The simplest form 

 of conidiophore in the first group is 

 a lateral or terminal hypha [iroducing 

 a single spore, which is abstricted and 

 falls off, after which another is formed. 

 In some cases, the spores may simiily 

 stick to the sides of the conidiophore, 

 and then a head of spores, held to 

 gether by mucilage, is formed. In 



other cases the conidia may be produced in Swellings on the Stem of Indian 

 chains, each conidium sticking to the Corn, 



one immediately behind it. The conidio- 

 phores may be branched, or given off in whorls, from 

 three to six in each 



Fk;. 23. UsTiL.viio May 



whose tip is also a 

 cases, the end of the 

 and covered with 

 mata, from each of 

 spores is formed. V.s.- 

 forms occur, as has 

 among the moulds, 

 blue moulds, Fcnicil- 

 on jam, bread, and 

 stances. The mildews 

 roses are also conidial 

 ous fungi. Spores 

 are intended to in- 

 a si)ecies; while the 

 usually [iroduced as 

 comes exhausted, are 

 favourable circumstances 

 often will not germinate 

 a resting i)eriod of 

 other two forms of 



whorl, from a hypha 

 conidiophore. In other 

 hypha may be swollen 

 small knobs, or. sfenJ/- 

 whichone or achain of 

 amples of these spore 

 been already stated, 

 such as the common 

 iiu/u spp. which grow- 

 other decaying sub- 

 of grapes, cotton and 

 stages of ascomycet 

 produced in this way 

 Fk.. 24. Gi:n.Mr- crease the numbers of 

 N \ I i.Ni; SiMiuK. ascospores which are 

 the food-supply be- 

 intended to carry on the species until 

 again arise, and consequently 

 until they have passed through 

 some months. With regard to the 

 conidial fructification, nothing further 



need be said here. It only remains to be added, before 

 concluding the description of the Ascomycetes, that some 

 species in this group may have both the first form and one 

 of the other two, in addition to the ascospore stage. 



The Basiiiiomvcetkh. This group of fungi may, for 

 the purposes of this article, be divided up as follows: — 

 Ustilagmeae. 

 Uredinales. 

 Hymenomycetes. 

 Gasteroniycetes. 

 In the first two groups, the basidium is divided up into 

 four cells by transverse septa. In the Ustilagineae, each cell 

 of the basidium gives rise directly to numer- 

 ous small sporidia. In the Uredinales, how- 

 ever, each cell of the basidium gives rise 

 to a lateral sterigma, and each sterigma forms 

 one sporidium terminally. In the other two 

 groups, the basidium is unicellular and forms 

 four terminal sterigmata, from each of which 

 a sporidium arises. (See Agricultural News, 

 Vol. IX, p. 94, Fig. 12.) 



The ustil.\hini;ae. The members of this 

 group are the well known 'smut' fungi of 

 various crops belonging to the grass family. 

 A full account of them was given in the Agri- 

 i-iiltvial News, Vol. I.\, p. 59, so that noth- 

 ing further need be added here. In Fig. 23, 

 a portion of the stem of Indian corn is repres- 

 ented, affected by the fungus Usti/ago Maydis; 

 it shows very clearly the characteristic swellings 

 produced by the fungus. Fig. 24 sliows a ger- 

 minating spore of the same fungus. It has 

 formed a septate basidium, from three cells of 

 which sporidia have been produced. 



The iTREms.ALis. This group of fungi 

 is entirely parasitic in habit, and its numb- 

 ers are often extremely specialized with 

 regard to the host pilants on which they can 

 live. The whole group has been exten.sively 

 investigated and is of great interest, as will, 

 it is hoped, appear later. One stage of the life- 

 history forms the ' rust ' disease of the leaves 

 of many different plants. The other gives 

 the ' cluster cups', also well-known 

 disease in many temperate coun- 

 tries. The actual damage done by 

 ditlerent members of the group 

 varies very largely. The forms best 

 known in this part of the West 

 Indies are : rust of cotton (I 'redo 

 (/ossypii, Aqy iciiltural NfU's, Vols., 

 'lV,p. 246:V, p. 1S3: VI, pp. 135, 

 174) rust of ground nuts (f'rcdo 

 'nricfiidis: see Agricnllural A'eics, 

 Vol. VIII, pp. 315 and 347), and 

 rust of cannas (I'redo cannae). In 

 this stage, the fungi form small 

 light- or dark-brown areas under 

 the epidermis of the leaves and green 

 ■stems of the host plant. When the 

 spores are ripe, the epidermis of the 

 host is broken and the spores are 

 freely exposed to the air. The 

 'cluster cup' stage is usually more 

 Fic. 25. I' liKuo LINEARIS. gJ,.(,^,]J^,. .^,-ij r.ften bounded by an 



(a) Tluee I'redospore.s. j ^^i^^ fringe of the whitish torn 



(b) <,ernnn,it,u^' I red.,- -^^^.j,^-^ ^f jj^g j^.^t j^^^ rpj^^ 

 .spores. ' ' 



rise to 

 signs of 



