Abstract
(1) In order to make the physiological constitution of the pithy tissue in root crops clear, the author investigated the process of the occurrence of pithy tissue in company with the corpulent growth in root by using radishes.
(2) As to the occurrence of pithy tissue in the radishes grown corpulent to a certain degree, it was first observed the disappearance of sugar in the large types of cells of xylem parenchyma which were far apart from the conducting tissue, and then among the neighbouring cells producing intercellular space lysigenously and schizogenously it gradually expanded till to assume the shape of pithy tissue.
(3) When the content of soluble matter in the roots was examined at the central part, the circumferential part and the middle part of both, it was ascertained that parenchyma in the middle part in which pithy tissue occurred, was less of its content in comparison with that in the other parts, and on the whole the more the degree of pithy tissue in he crops was, the more the content in them was lowered.
(4) Pithy tissue occurred when the length of leaves, the number of leaves, the weight of roots, the diameter of them and so on increased rapidly while the rate of T/R decreased, and during this period the cells of parenchyma reached to the maximum in size and number, and the content of the soluble matter indicated the minimum.
(5) Ones which have a great deal of pithy tissue can be found generally among those heavy in weight and wide in diameter, but among which the rate of T/R is greater the occurernce is less.
(6) The first step to the occurence of pithy tissue will be ascribed to decrepitude of the cells of parenchyma, and it will be concluded that mainly due to the rapid growth of the cells the content of the matter falls, and in addition to that by bringing out the difficulty in supply of nutrition from the conducting tissue it causes a sort of the starving condition.
