Rice Disease caused by Ustilaginoidella graminicola. 
BY 
Ed. ESSED, B.Sc. (Edin.). 
With Plate XXXI. 
R ICE has for a long time been cultivated in Guiana, but it seems 
that nothing was known before of any disease destroying rice crops, 
until about a year ago, when a rather serious disease broke out among the 
rice fields. Care was bestowed on it by the staff of the experimental station, 
where it was investigated without the cause being found ; at least in the 
annual report, 1909, I read that neither the Government botanist nor the 
Agricultural instructor succeeded in finding the cause of the disease. I am 
well pleased to be able to communicate the positive results of my research. 
The plants are often attacked in their most tender age, and then the 
whole crop may come to nothing, the haulms drying up long before the time 
of flowering ; or they may be taken hold of shortly before flowering or at 
the time of flowering, and then only a small percentage of the flowers may 
escape destruction. Many apparent fruits are found to be empty husks. 
The disease first manifests itself by dark-brown intercostal spots with 
yellowish margins appearing on the leaves and sometimes on the sheaths also 
(see PI. XXXI, Fig. 1). The general aspect is that of ‘ Rust’. Besides the 
rice, another grass, a species of Panicum , was found to be suffering from 
the same disease. 
If a fragment of a leaf, having been stained with eosin and passed 
through alcohol of progressive strengths, carbol-xylol, and xylol, and at 
last enclosed in balsam, be brought under a low power, the dark spots will 
be seen to consist of a dark-brown centre — where the epidermis may be 
absorbed — gradually passing to a yellow periphery with indistinct lines of 
demarcation. Hyphae are seen to run through and between the epidermal 
cells, branching in all directions, entering and emerging from the stomata ; 
spores of the same types as met with in the two foregoing species are found 
lying on the leaf, and crowded in and between the epidermal cells and in the 
emergences. The brown spots are nothing but pegmatia, cementing, as it 
were, the cells attacked and so rendering the cell-walls quite indistinct (see 
[Annals of Botany, Vol. XXV. No. XCVIII. April, igix.] 
