174 



THE AGRICULTURAL NEWS. 



May 28, 1910. 



FUNGUS NOTES. 



FiC. 29. Dll'LODIA CACAOirOLA. 



Longitudinal Section of P3'enidia 

 and Stroma. 



THE CHIEF GROUPS OF FUNGI. 

 Part VII. 



The Fuxia Lmi'erfecti. This is the la.st grou|i of fungi 

 to be considered. It contains many genera and species that 

 vary immensely in form, but which are all characterized by the 

 possession of conidia onlj', and by not forming any higher 

 fructification, such as an ascospore. , ^lost of them are species 

 whose life-history has nat been completely worked out, 

 though they are sus[)ected of being stages in that of various 

 fungi belonging to known or unknown species of the Asco- 

 uiycetes. Of late years, many of them have been more fully 

 investigated, and in consequence have been removed and 

 placed in different groups of the Ascom_ycetes. (See J(/7-i- 

 niltaral News, Vol. IX, p. 1+2.) The group may be subdi- 

 vided as follows: — 



Sphaeropsidales. 

 Melanconiales. 

 Hyphomycetales. 

 The sphaeropsi- 

 dales. These fungi 

 produce conidia borne 

 at the tips of slender 

 conidiophores. The 

 conidiojihores, and 

 frequently paraphy- 

 ses, are contained in 

 pycnidia, which often 

 closely resemble the 

 perithecia of the 

 Pyrenomycetes. Two 

 of the families in this 

 cohort may be shortly considered. 



In the Sphaerioidaceae, the pycnidia are always black in 

 colour, and of the consistency of leather or charcoal. They 

 may be free and superficial on the substratum, immersed in 

 it, or grouped on a stroma. The conidia may be unicellular 

 or nnilticellular, hyaline or dark brown. The minor charac- 

 ters, such as the 

 presence or 

 absence of a 

 stroma, and the 

 colour of the 

 spores, serve to 

 divide the differ- 

 ent genera from 

 one another. To 

 this family be- 

 long the species 

 Diplodia cacaoi- 

 cola, causing die 

 back and brown 

 pod of cacao 

 (Figs.29and30), 

 Jjo1rt/tidijilodi>i 

 sp., causing root 

 disease of cocoa- 

 nuts, and one or 

 two other allied 

 .speci'is of economic importance in these i.slands. 



In the Xectrioidaceae, the pycnidia are Heshy in con- 

 .sistency, and frequently brightly coloured, never black; they 

 may be free and suiicrficial on the substratum, or grouped 

 in a stroma.. The conidia may be uni- or multicellular, 



Flo. 31. COLLETOTRIIHIIM LUMFICUM. 



Longitudinal Section of a Pustule, showing 

 Conidiophores, Conidia and Hairs. 



hyaline or slightly coloured. To this family belongs the genus 

 Ascliiisoniii, two species of which are parasites on the white 

 fly in Florida. 



The members of these two faniilies probably represent 

 stages in the life-history of different members of the Sphaeri- 

 ales and Hypocreales, respectively, in the Ascomycetes. 

 (See Aijricultimxl Xeirs, Vol. I.V, p. 12fi.) 



The melanconiales. In this cohort, the conidia are pro- 

 duced on a more or less developed cushion or stroma, beneath 

 the surface of the substratum. These cushions finally break 

 through to the surface, in most cases, and form superficial 

 pustules of spores, often coloured in the mass, as in the genus 

 Colletotrichuiii, where they are frequently pink or yellow. The 

 stroma is generally black, and this gives the fructifications 

 a black appearance when young. In the case of CoUetotri- 

 r/iuiii falcatuiii -they remain black. In other cases, the 

 spores are e.Ktruded in a tendril and are dark brown, 

 or black in the mass, as in the genus Melanconiiim The 

 cohort contains only one family — the Melanconiaceae, but 

 this embraces several important economic genera. It contains, 



for instance, the an- 

 thracnose fungi of the 

 genera Colletotrichum 

 and Gloeosporiuni. 

 Collctotrichumi/ossypii 

 causes anthracno.se of 

 cotton, V. lu.iificum^ 

 jT.-rt^/ witches'brooai of cacao 

 ™ / (Fig. 31), and in addi- 

 tion several other spe- 

 cies occur on cacao- 

 pods. (See West Indian 

 J]nlleiin,Yo\.X,l).25\.) 

 C. falcatvm causes red 

 rot of sugar-cane, and 

 Gloeosporium m. usa- 

 riim, anthracnose of 

 bananas. The melanco- 

 nium stage of 7'richo- 

 sphai'i -ia sa ccha i i — the 

 Fii! 30. Diplodia cACioicoLA. rind disease fungus of 

 Longitudinal Section of a Pycnidium sugar-cane, was also at 

 showing Conidiophores, Conidia and one time thought to be 



Paraphyses. 



=yk: 



Fn;. 32. Fusarium lycopers 



(I) Diplocladium Stage. 



(II) Fusarium Stage. 



a separate fungus and 

 includ-jd here. Pesta- 

 loixia palniaruni, which 

 attacks the leaves of cocoa- 

 nut palms, is another mem- 

 ber of this group. 



The uyphomyi'ETai.es. 

 These fungi are mainly 

 superficial, sometimes only 

 partly so; rarely endopara- 

 sitic on insects. The hyphae 

 are often profuse, and bear 

 free, naked conidia These 

 are for the most part the 

 fungi known as mildews 

 and moulds. The cohort 

 embraces four families. 

 In the Mucedinaceae, 

 the hyphae and conidia are 

 hyaline, or clear-coloured; 

 never brown or blackish. 

 The family is subdivided 

 on the characters of the 

 conidiophores a n d the 



