SEASONAL DIMORPHISM OF CHAMAEPHYTES 



211 



H 



Fig. 3. Life cycle ofPoterium spinosum. 



(a) A small absolute brachyblast (i) on the lower part of a dolichoblast developed 

 during the previous spring. 



(b) New winter leaves are formed on the same brachyblast which resembles a 

 small rosette (5). The renewal buds (3) appear on older branches. 



(c) The inflorescence (3) appears at the apex of the brachyblast. The young 

 dolichoblasts (6) emerge from the renewal buds. 



(d) The new dohchoblasts bearing spring leaves (4) reach their maximal height. 

 The autuimi and winter leaves already shed. 



(e) The spring leaves of the same doHchoblasts already shed. New brachyblasts (7) 

 bearing summer leaves developed in their axils. 



leaves absent 

 leaves developing 

 leaves persisting 

 leaves being shed 



Upper row -autumn and winter leaves 

 Middle row- spring leaves 

 Lower row -summer leaves 



of these dolichoblasts. The lower leaves are larger with many lobes while 

 the upper ones are bractlike, simple and linear. Leaf shedding starts in 

 April from the lower parts of the dohchoblasts and goes on gradually 

 during the late summer in an acropetal direction until the autunm when 

 practically no leaves remain on the stems except from a few flower bracts. 

 During the late summer the axillary buds at the lower part of the 

 dohchoblasts start developing into tiny rosette-hke brachyblasts. Although 

 no elongation takes place they do not stop growing, new leaves are formed 

 at their apex and the older ones dry out and are gradually shed. In the 

 autumn, part of them starts elongating, yielding the new dohchoblasts, 

 while the others dry out and drop. The upper portion of the dolichoblasts 

 die back almost to their base during their second winter. 



