Studies on the Trichomes of some Compositae II. Phylogeny and Classification

On the basis of the evidences from structural patterns, modes of development and metamorphic variations, the vegetative trichomes of the Compositae are shown to consist of four systems viz., I. Filiform System II. Macroform System III. M-Multiseriate System and P-Multiseriate System.

As Trichomes comprise more than one system, their phylogeny and classification needs to be studied separately within each system.

Evidences from the metamorphic variations and from the trichomes of the hybrids are shown to be of value in tracing the relationships. Netolitzky's (1932) phyletic dicta-which in general conform to the evolutionary principle 'simple to complex'-are considered to be useful in recognising the general primitive or advanced condition of a trichome within its system.

Within the systems, trichomes are shown, to be classifiable into the three morphological groups 'Papillae', 'Scales' and 'Hairs' adopted by Cowan (1950) for the trichomes in Rhododendron.

Studies on the trichomes of vascular plants in general are emphasized so that information could be available on the total number of their systems and distribution which will not only be of morphological value but also bf taxonomic significance.