396 Dastur. — The Mode of Infection by Smut in Sugar-cane. 
Having established the fact that infection can take place through 
unwounded tender buds and through wounded old buds, the next step was 
to find the exact place through which the infecting germ-tube enters the 
host tissues. It was suspected that infection takes place through unthickened 
scale hairs, because the cavities of the hairs of the inoculated eye-buds were 
found to be filled with unseptate or* very sparsely septate hyphae, and in 
some cases germ-tubes from what looked like sporidia were found to have 
penetrated the hairs. 
Ultimately a few cases were found which conclusively proved that 
infection takes place through the scale hairs. In one particular case a spore 
had germinated on the surface of a thin hair and from the end of the pro- 
mycelium a sporidium had developed. From this sporidium, which was 
still attached to the promycelium, a fine germ-tube was developed, which 
pierced the thin wall of the hair. In the lumen of the hair the fine germ- 
tube broadened and travelled downwards (Fig. 6). 
Other very clear cases (Figs. 7-9) of sporidia penetrating the hairs of 
the scale leaves by means of their germ-tubes have been observed from 
time to time. At times the hair reacts to the entrance of the germ-tube by 
developing a plug or thickening on the inner wall (Figs. 8 and 9). Whether 
the plug prevents infection is not definitely known. A few cases, however, 
have been observed in which the germ-tube was found beyond the plug. 
It is only the unthickened hair that the sporidium is capable of infect- 
ing (Fig. 10 ,a-d). Hairs with thickened walls (Fig. 10, e-i) have not been 
found to be infected, though spores and sporidia have been found to be 
lying on them. So far the germ-tube from the sporidium has not been 
observed to enter directly the epidermal cells. 
Inside the hair, the hyphae from the sporidium give out branches 
which at times completely fill the lumen of the hair. From the basal part 
of the hair the hyphae enter adjacent epidermal and sub-epidermal cells 
(Figs. 4 and 5). In the tissues of the scale leaves the mycelium is intra- 
cellular and consists of long strands of hyphae which are sparsely septate 
(Fig. 3). In the young stem of the leaf-bud the mycelium is at first both 
inter- and intra-cellular, but ultimately it is chiefly intercellular. The 
mycelium from the outer scale leaf travels downwards, enters the young 
stem of the leaf-bud through the leaf base, thence it travels up the inner 
leaves and the growing-point and also enters the main stem through the 
node. In some cases the hyphae in the outer scale leaf directly enter the 
inner scale leaf, the outer epidermis of which is closely adpressed to the 
inner epidermis of the outer scale leaf. 
Conclusion. 
The experiments conclusively prove that direct infection of ‘ thin ' 
varieties of cane can take place through tender buds, but not through old 
