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SUGAR-CANE DISEASE. 



Extract from Keic Bulletin. 

 Report on "Root Disease" of Sugar-Caxe from Barbados. 

 By GEORGE MASSEE, Royal Gardens, Kew. 



The stools of sugar-cane sent to Kew by Mr. Bovell from Barbados, 

 for the purpose of ascertaining the cause of the " root disease," arrived 

 in excellent condition tor that purpose, and an examination of them 

 demonstrates conclusively that the disease is due to a parasite fungus 

 known as Collet otrichurn falcatum, Went. The fungus cannot effect 

 an entrance through the unbroken surface of the stem of the sugar- 

 cane. But the conidia germinate on decaying lateral shoots, or the 

 ragged base left by fallen leaves. Its entrance into the living portion 

 is indicated by a bright red coloration of the fibro-vascular bundles, 

 the colour subsequently extending to the ground tissue. 



When an entrance has been effected the hyphae spread rapidly 

 throughout the length of the cane, and after a time the fructification 

 ruptures the epidermis in the neighbourhood of the joints, and appears 

 on the surface as a more or less effused, black, minutely velvety patch. 



Microscopic examination shows the velvety appearance of the fruit- 

 ing patches to be due to the presence of numerous rigid, dark-coloured 

 hairs, springing from a dense basal weft of colourless hyphse ; these 

 latter also bear large numbers of minute, colourless conidia, or repro- 

 ductive bodies. The conidia are capable of germinating the moment 

 they are mature, and being produced quickly and readily disseminated, 

 easily infect neighbouring plants. 



A second kind of conidia are formed on the oldest portions of my- 

 celium present in the tissues, two or three large globose conidia being 

 frequently found on the hyphae present in a single cell of the cane. 

 These internal conidia can only escape when the cane in which they 

 exist has become thoroughly decayed. The fungus, under normal con- 

 ditions, attacks the above-ground portions of the cane, the "root 

 disease" condition being a modification of the normal form, called into 

 existence by the method of cane cultivation adopted. 



A careful examination of all the canes forwarded shows that the 

 portion buried in the ground contains much more mycelium than that 

 above ground ; the mycelium in the root is also more mature, frequently 

 producing enormous quantities of conidia in the cells. In some in- 

 stances the root was rotten and decayed, the disintegration being 

 effected by the fungus ; nevertheless there is not the slightest evidence 

 to favour the idea that the disease originated after planting. Many of 

 the small roots contained a large quantity of mycelium, but it was 

 evident in every case that this had passed from th<* stock into the root. 

 On the other hand, everything points to the conclusion that the por- 

 tions of the cane used for propagation already contain the mycelium of 

 the fungus, although its presence may not be indicated externally, and 

 that the mycelium present in the buried portion of the cane, favoured 

 by darkness and moisture, develops at an abnormal rate, thus assum- 

 ing the character of a disease, which in its intensity is foreign to the 

 fungus when developing under normal conditions. Two additional 

 species of fungi, not in any way connected with the disease, were com- 

 mon on fading leaves of the canes ; the one, a species of Uhcetostrotna, 



