The mode of growing of foliageleaves, sheath-leaves and bulb-disc in Hyacinthus orientalis

During the research on ‘The periodical circumferential growth of the bulbs of hyacinths’ (A. H. Blaauw 1923) the question presented itself how the periodical growth in breadth of the foliage-leaves and sheath-leaves is effected, viz. whether it is due to cell-division and extension or to extension only. This question was the starting-point for the following research. It being necessary to study the growth in breadth in connection with the growth in length, the latter was first examined.