SECTION Vr. — NATURAL ENEMIES OF TIIR FROGHOPPER. 93 



Thus it will be seen that birds eat froghoppers, but they also eat 

 lizards, which in turn eat froghoppers. The mongoose cats birds, which 

 eat froghoppers, and as such it is undesirable. But the mongoose also 

 «ats rats, which eat birds, which eat lieards, which eat spiders, which 

 eat Syrphid flies, which eat froghoppers. What conclusion can be drawn 

 from this ? 



It is hoped that an examination of this diagram will disillusion those 

 who speak of the "Introduction of New Enemies" as if it were a remedy 

 the obviousness of which was only exceeded by its simplicity and 

 certainty of success. 



SECTION^ V^II. 



THE ROOT DISEASE OP SUGAR CANE. 

 It is not the purpose of the presenb report to give a complete account 

 of the root-fungi of sugar-cane. Such a work is best done by an 

 experienced mycologist. Only a sufficient outline will be given here to 

 enable the planter to recognise the chief root-fungi, in order that he can 

 realise for himself the part they play in the production of blight. 



For most of the technical information in this Section I am indebted 

 to the writings of Nowell, .Johnston, Bancroft, South, and others 

 mentioned in the bibliography at the end. 



FUNGI CONCERNED. 



We have apparently two distinct groups of fungi attacking the roots 

 of cane in Trinidad (1) The Marasniius type and ('2) the Odontia- 

 Himantia type. 



Quite recently Carpenter (1919) has described a root fungus Pythinni 

 sp. causing a form of root disease in canes in Hawaii but no search has 

 yet been made here for this fungus. 



Marasmliis type. The most obvious visible sign of the presence of 

 this fungus is the matting of the leaf sheaths, particularly near the base 

 of the stem, by a white, dried-paste-like mycelium (Plate VII). This is 

 the vegetative part of the fungus and grows in living or decaying tissue 

 according to conditions. The spores of these fungi are produced on 

 small mushrooms or toadstools (Plate VIII) which are however not 

 frequently found. The various species concerned differ in small details 

 such as the size of the mushroom, the^number of rays beneath the top 

 and the colour of the stalk, but all are apparently more or less similar 

 in effect. 



The Odontia fungus in its vegetative stage also mats down the basal 

 leaf-sheaths of the cane, but on pulling them apart a feathery fungus is 

 seen (Plate IX) which when examined with the microscope is found to 

 contain numerous minute stellate crystals. This form is found between 

 the matted sheaths only, in positions hidden from the ligiit, and has been 

 known as Hiinantia stellifera. 



