This study was made in 1963, in order to clarify the affection of the sugarcane plant in early period of its growth, caused by the following three species of nematodes, Helicotylenchus dihystera (Cobb), T ylenchorhynchus sp. and Meloidogyne incognita Kofoid et White.
1. The sugarcane plants cultured in the soil containing Helicotylenchus dihystera were injuredd to some degree in their roots but slightly in their stumps. That is, the decrease in the dry weight of the root was 21.7 per cent., while those of the stump, stem and leaves were 10.7, 16.4 and 8.2 per cent. respectively (Table 2, Fig. 3) .
2. The affection of the sugarcane plants cultured in the soil containing T ylenchorhynchus sp. was much higher than that caused by H. dihystera. The damage percentages in the dry weight of the stump, stem and leaves were 17.8, 21.7 and 19.1 per cent. respectively. The sugarcane plants affected by this species produced a large number of roots, though these roots were distinctly light, decreasing to 35.6 per cent. in their weight (Table 3, Fig. 3) .
3. In case that the sugarcane plants were cultivated in the soil containing both species, H. dihystera and T ylenchorhynchus sp., 38.5 and 41.0 per cent. decreases took place in the respective stem and leaves, which were different significantly from those in the check containing no nematode. However, in the dry weight of the root and stump of the treated plants, only 10.8 and. 5.8 per cent. decreases were observed respectively (Table 4, Fig. 1 and 3) .
4. The injury of the sugarcane plants caused by Meloidogyne incognita was much higher than that caused by the preceding two species, H. dihystera and Tlyenohorhynchus sp. The data showed 26.8, 28.2, 56.0 and 28.5 per cent. decreases in the dry weight of the stump, stem, root and leaves respectively, making a significant difference from the result of the check (Tables 5 and 6, Fig. 2) .
5. From the result of the author's experiment, it can be considered that the affection of the sugarcane plants in fields may substantially be little so far as it is concerned with the species Helicotylenchus dihystera alone. The species, Tylenchorhynchus sp. seems to be the most important one among many kinds of nematodes found in the sugarcane fields in Ckinawa, as well as, another species, Meloidogyne incognita.

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