ИСТИНА

Since Shimper (1836), three leaf formations on the generative shoot have been distinguished:cataphylls, foliage leaves and hypsophylls. In spite of structural and functional differences, all three leaf categories have a common morphological nature. A comparative morpho-anatomical analysis of different leaf formations of generative shoots in four winter- and summer-green species of Helleborus was conducted. The results obtained clearly show that the leaf heterogeneity is caused by (1)leaf differentiation from different parts of leaf primordia,(2) early divergence in growth and developmental pathways. So it is more logical to compare the cataphylls with leaf base of foliage leaves and bracts with lamina, because these leaf types are the results of the realisation of the developmental programmes of either the entire leaf primordium or of its part.