The very fast development of maize plants at Ibadan, Nigeria, has been described and an attempt has been made to obtain a better understanding of their development with the aid of a growth analysis. Two varieties of maize have been studied, which, again during this experiment, proved to have a very different yielding performance, in spite of a rather similar vegetative development. It was shown that Lagos White, the local variety, produced approximately 2000 lb./acre and ES 2 3000 lb./acre.

From approximately the ninth week onwards the ear starts rapid development, and the retention of a larger functional photosynthetic area by the introduced variety ES 2, from the eighth week onwards, seems to be the major factor controlling its higher production of dry matter in the latter part of development, when compared with Lagos White.

On the average, n.a.r. had similar values in both varieties and had similar deviations at various stages of development; external or internal factors could not be separated. The l.a.r. indicated that, certainly in the latter part of development, ES 2 plants and Lagos White plants had a similar leaf area per gramme of dry matter; but ES 2 had more of both. This factor stresses the similarity of efficiency in both photosynthetic mechanisms.

The l.a.r shows in clear terms the difference between the two varieties grown at equal spacing. The variety ES 2 still increased its leaf area with its additional laminae, when Lagos White, which had a more rapid loss of leaf by senescence, had come to a standstill. The more pronounced longevity of the photosynthetic area in ES 2 appears therefore the major determinant of the higher production of dry matter by this variety. The possible significance of variation in longevity of leaves had been pointed out already in 1929 by Boonstra, who found some evidence of an association of longevity of leaves and high yields in four varieties of oats.