SEASONAL DIMORPHISM OF CHAMAEPHYTES 



209 



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IV V VI Vil VIII IX 



Fig. I. Life cycle of Thymus capitatus. 



(a) The lower part of a dolichoblast developed during the previous spring bearing 

 small absolute brachyblasts (4). 



(b) One of the brachyblasts of the same branch which has started elongating, 

 (i) Summer leaves, (2) winter leaves. 



(c) The same elongating brachyblast reaching its maximal height. (3) Tlie 

 inflorescence. 



(d) The same branch; the winter leaves already shed and the new brachyblasts 

 developed at their axils (4) which form the whole green cover of the plant. 



H leaves absent 

 leaves developing 

 leaves persisting 

 leaves being shed 



Upper row -winter leaves 

 Lower row -summer leaves 



whole summer. The plant flowers in June and sets fruit in August (Fig. 2). 

 (c) Poterium spinosnm. While the inflorescences of Thymus and Teucrium 

 are developed on the dolichoblasts those o( Poterium are developed on the 

 brachyblasts which are absolute and permanent. The dohchoblasts generally 

 are developed from renewal buds and start growing late in February. Their 

 growth rate is very rapid during March and April and they may attain 

 their maximal height at the beginning of May. Branching takes place on 

 their upper portion and the apices of the small branches taper into spines. 

 The larger spring leaves of these dohchoblasts are gradually shed in an 

 acropetal direction from the middle of May to the end of July. In the axils 

 of these leaves small brachyblasts are formed druing April. They look like 

 half open buds and bear small summer leaves. During the summer the older 

 leaves of these brachyblasts are also gradually shed while new ones develop 

 at their apices. This process goes on during the autumn but the new leaves 

 which are formed from October onwards are larger and resemble the 



