6 
Tansley and Fritsch. 
by throwing down bunches of strong roots from the nodes at which 
branches have arisen. If it should be overwhelmed by blown sand, 
as often happens, its great branched system of wide-stretching, 
firmly rooted shoots enables the plant to survive, and its quick 
growth soon brings young shoots to the surface to begin again their 
work of covering the sand with vegetation. In this respect it 
resembles its congener Psamma armaria , which does identical work 
on our northern sandy coasts. Like Psamma, its power of growing 
to the surface of and binding the heaps of freshly blown sand 
enables it to form dunes if the supply of blown sand is considerable, 
but on the part of the Ceylon coast with which we are dealing dunes 
are not common, 1 probably because the fresh sand thrown up by the 
waves is not very abundant. 
Fig. 3. Ipomcea biloba. Leaves to shew variation in size and shape according 
to habitat. A and B, Luxuriant forms from mud at Malacca. C, Normal 
leaf. I), Stunted form from very arid sand. £ nat. size. 
Ipomcea biloba is a very variable plant according to its situation. 
Its seeds can germinate in the most arid sand, but the growth of 
1 They exist in the neighbourhood of Hambantota, but Ipomcea 
does not occur there. 
