Kaszab Zoltán (szerk.): A Magyar Természettudományi Múzeum évkönyve 64. (Budapest 1972)

Szujkó-Lacza, J. ; Fekete, G.: A survey of the plant life-form systems and the respective research approaches IV. Taxonomic aspects of the life-form protection of the embryonal and meristematic tissues in the dormancy stage

Table 1 n Lian Epiph. Suce. Mg Ms Mi N Ch H G HH Th Quaternary 510 4 0.4 0.2 1 10 11 7 9 34 4 3 16 Neogene 560 8 1 3 21 26 14 2 14 2 5 5 Paleogene 785 12 1 4 27 28 12 2 8 2 3 1 Cretaceous 149 7 5 7 23 17 13 3 18 9 6 On the basis of the simple statistical analysis, he established that "The lifeforms are obviously of different ages. The youngest life-forms are Chamaephytes, Geophytes, and Therophytes with maximum values in the Quaternary period. Earlier than these are the Nanophanerophytes and Hemieryptophytes, the development of which especially took place in the Neogene. Still earlier are the Microphanerophytes and Lianes, the maximum development of which falls in the Paleogene. The oldest bfe-forms are Megaphanerophytes and Mesophanerophytes, whose development culminated in the Cretaceous period". HANSEN connected the ascendancy of the species with a new

7 life-form and parallel with this the reduction of stature from the Megaphanerophytes to the Therophytes with the gradual and continuous deterioration of the climate, from the Paleogene to the Quaternary. The Cretaceous introduces the dicotyledonous genera (mainly arboriform species), with their further extensive evolution in the Paleogene. ANDREÁNSZKY (1954b) makes a similar statement: the appearance of the dicotyledons resulted at the same time in the conquest of enormous areas, coincidently with a considerable increase in the number of species and lifeforms. According to SEREBRTAKOV (1955), who, like RAUNKIAER, regarded life-forms as the result of climatical adaptations, the length of the life of the main axis of the plant, namely that of its epigeal part, determines the entire habit and stature, and characterizes also the whole life-form evolution. During the evolution of a convergent character of the life-form, trees of a medium stature, or according to SEREBRIAKOV multitruncate trees (treated as a distinct life-form), can be derived from the reduction of the gigantic tropical trees. With the unfavourable trend of the climate and the reduction of stature, also the annual growth and the age of the plant decrease. Reduction can be followed within any given ordo. In the Ericales, for instance, it can be traced from the arboriform taxa through the subherbaceous life-forms to the Hemieryptophytes of 2-5 years life span in some genera of the family Pyrolaceae (e.g. Pyrola and Ramischia species), indeed, to the Geophyton life-form (e.g. Monotropa hipopytis). SEREBRIAKOV'S life-form evolution concept agrees to a great extent with the assumption of stature reduction in plants accepted on the basis of studies (of a different aim) made on paleobotanical finds and recent taxa. SEREBRIAKOV'S life-form evolution scheme is based on innumerable observations and experiments ; the method is termed by him and SEREBRIAKOVA as comparative or experimental ontomorphogenetics. The morphogenesis of a taxon, in the entire extent of its geographico-ecological amplitúdó, is observed, wherein the behaviour of the species within extreme conditions may render information also on the trend of the lifeform evolution. The method can be enlarged to include similar studies on related species. Experimental ontomorphogenetics means the introduction of the species