19 



NOTE ON THE CECOLOGY OF SPIlNIFEX 

 SQUARROSUS l* 



By P. F. Fyson, B.A., F.L.S., AND M. Balasubrahmanyam, b.a. 



The question discussed in this paper arose in the course of an 

 investigation into the water and soil-relations of the marine strand 

 vegetation of Madras. One of the most important species of the 

 strand formation is Spinifex squarrosus L. It occurs on low sand- 

 dunes as close as 20 yards only from the sea, but always raised a 

 few feet above high-tide level. It usually grows by itself, but in 

 open patches Cyperus arenarius Ketz. and Launasa pinnatifida Cass, 

 sometimes occur. 



The plant spreads over the sand by horizontal shoots which root 

 at the nodes, usually beginning with the second and third node from 

 the growing end. The adventitious roots are thick and run more or 

 less vertically downwards for one or two feet, with only small rootlets. 

 Eoot-hairs are conspicuously developed on the oldest part near the 

 surface of the soil and seem to be persistent there. A few inches 

 below the surface of the ground there are usually none, or only 

 shrivelled dead hairs, and the root is sometimes thinner because of 

 the exfoliation of the outermost layers of the cortex after the forma- 

 tion of an exodermis. The youngest part has no root-hairs, as a rule ; 

 the root being quite smooth for one or two inches behind the tip, 

 then becoming slightly lumpy on account of branch roots pushing out 

 from below, but still without any sign of root-hairs. 



If a plant be dug up without breaking the roots, and grown in a 

 jar with some roots in water, root-hairs appear on young roots close 

 behind the growing point, but not on older roots. 



Sections of this lowest region shows the root surrounded by a 

 highly refractive substance, which is apparently secreted by the cells 

 of the piliferous layer. This layer and its secretion can be traced 

 quite easily under the root-cap back to the earliest stage in the 

 differentiation of root-cap and piliferous layer. The cells are at first 

 isodiametric but soon become elongated radially, taking on the 

 general appearance of secretory tissue. There are no intercellular 

 spaces, the cells are narrow the protoplasm is dense without vacuoles 

 and the nucleus large and situated about the middle. The outer wall 

 is irregular in outline, and beyond it the secretion is marked by 



Paper read at the Indian Science Congress, 1919, 



