



THE 



journal of Indian Botanp. 



Vol. I. DECEMBER, 1919. No. 4. 



THE PHYSIOLOGICAL ANATOMY OF THE 

 PLANTS OF THE INDIAN DESERT 



BY 



T. S. Sabnis, B.A., B.Sc. 



St, Xavier's College, Bombay. 



(Continued from last issue.) 



Portulaca quadrifida, L.—{Cont.). The pith is composed of 

 thin-walled cells filled with starch granules. 



The two features, viz : the peripheral position of the aqueous 

 tissue and the central position of the assimilatory tissue near the 

 vascular bundles are quite significant. The acqueous tissue from its 

 peripheral position is able to absorb moisture easily and carry on its 

 function without being disturbed by any other tissue situated outside. 

 It further protects the assimilatory tissue from the injurious effects 

 of intense light and heat. 



Were the assimilatory tissue peripheral, the products of assimila- 

 tion would have to travel a long distance before they could reach the 

 vascular bundles ; thus the distribution of the products of assimila- 

 tion would be greatly retarded. Therefore either the assimilatory 

 tissue should be centrally placed near the vascular tissue or the 

 aqueous tissue should be reduced, so that the distribution of the 

 assimilatory products may go on rapidly. 



It is possible that the assimilatory tissue enclosed by an 

 extensive aqueous tissue may not get enough light, but this cannot be 

 helped. As the development of an aqueous tissue is necessary for 

 succulent plants, the central position for the assimilatory tissue is the 

 only position, so that both the tissues can carry on their work 

 without being interfered with by the other. 



