REVISION OF ANACYCLUS 91 



once all the component members can be identified, a combination of the main elements of 

 Reitbrecht's 'Matricaria-gmppe' with the 'Achillea-gmppe' will form a natural monophyletic 

 group in the Anthemideae. 



Morphology 



This section provides a comparative review of the principal morphological features in Anacyclus, 

 which are described formally in the taxonomic descriptions. An attempt will be made to emphasize 

 the evolutionary trends so that an understanding of primitive and advanced character states will 

 provide a detailed basis for the phylogenetic reconstruction (p. 105). 



Habit 



Most species of Anacyclus are annuals, a condition found in several of the north temperate genera 

 of the Anthemideae (Hey wood & Humphries, 1977). Phylogenetic analysis suggests that this is 

 a derived condition as an adaptation for survival in dry, disturbed habitats. Several species, e.g., 

 A. nigellifolius, A. latealatus, A. maroccanus and A. linear ilobus, have restricted distributions, 

 but the remainder have relatively wide-ranging distributions in weedy habitats. In natural sandy 

 areas of the desert, the most extreme developments of prostrate annuals with reduced stems and 

 leaves are seen in A. monanthos and to some extent in A. homogamos. In dry roadside or waddy 

 habitats the vigorous, tough and leafy stems of A. radiatus and A. clavatus are among the largest 

 growth forms to be encountered in the genus. A. nigellifolius, from dry rocky places in the eastern 

 Mediterranean, represents another reduced annual habit with short erect stems (few or no 

 branches emerging from the middle or above the centre of the main stem) and deeply dissected, 

 small leaves. 



Many species of the Anthemideae are woody or herbaceous perennials. A. pyrethrum, the only 

 perennial species in Anacyclus, is a highly specialized montane and subalpine herbaceous per- 

 ennial from open grassland and rocky places in the mountains of Morocco, Algeria and Spain. 

 It is short-lived, with a dwarfed submerged stem fused with a long taproot to form a basal 

 woody caudex, from which leaves and then flower-bearing peduncles emerge annually. Cross- 

 sections of the caudex from the field suggest that most plants live for two or three or sometimes 

 up to five years, although cultivated specimens can survive for a considerably longer period. 



The leaves and peduncles emerge as a prostrate rosette from the centre of the caudex during 

 the spring and persist until the end of the summer. The submerged caudex seems to be an adapta- 

 tion to the dense snow cover and severe winters of the Atlas mountains. 



Leaves 



In most species the leaves are arranged alternately on the stem. However, in one or two species, 

 e.g. Anacyclus pyrethrum, the leaves are so tightly whorled in a basal rosette that this arrangement 

 is obscured (Fig. 12). Some evidence of leaf rosettes can also be seen in annuals, e.g. A. radiatus 

 subsp. radiatus (Fig. 17) where the basal internodes are very short. A. pyrethrum (Figs 2 A, 12) 

 appears to have heteromorphic leaves, because there are only massive tripinnatisect basal rosette 

 leaves and pedunculate bracts present. A general gradation in leaf size and dissection is absent 

 because of the reduced habit in this species. 



The leaves of Anacyclus are invariably pinnatisect, whereby the primary divisions cut right 

 through to the axis. The leaves range in dissection from 1- to 3-pinnatisect, depending on their 

 position on the plant, e.g. main axis or peduncles, and, to a lesser degree, the differences between 

 species, e.g. the small, 1- to 2-pinnatisect leaves of A. nigellifolius (Figs 2 J, 26). The leaves are 

 usually differentiated into lamina and petiole, although the latter is often absent or reduced. 

 The most distinctive petioles are the persistent cuneate types found on the rosette leaves of 

 A. pyrethrum (Figs 2 A, 14) and A. monanthos subsp. monanthos (Fig. 2 B). The lamina is usually 

 more or less flat, but is distinctly terete in the leaves of A. pyrethrum (Figs 2 A, 12). There is a 

 considerable variation in leaf size, the largest leaves being found in the robust annuals A. radiatus 

 subsp. radiatus, A. x valentinus (Fig. 2 G) and A. linearilobus (Fig. 2 I) and the smallest in the 



