XVI International Botanical Congess

The cases (after human skin injury by a cactus spine) of the granulems formation with the subsequent morphogenesis of the bristles are known.The bristles formation from the plant cells callus that is formed in human skin are revealed. The comparision of bristle structure with that of the cactus (the cause of the trauma) revealed their similarity. But some peculiarities in the structure of bristle can be explained only by the change of the tissue differentiation program in parasitism condition. Change in the development program for some cacti epidermal complex (Brown,1920) and wood (Mauseth,Plemons, 1995) is known. This peculiarity together with the areol structure (the latter consists of a mass of meristem forming spines and hairs growing by the basal part and can cause callus appearence in the trauma area) are the structural basis of the cactus parasitism ability.