iqiq] 



WATERMAN— ROOT SYSTEMS 



37 



were found growing in the water on the edge of a pool, with no 

 apparent effect on the roots. Observations near Miller, Indiana, on 

 P. pumila and Populiis deltoides, seemed at first to show such effects 

 (fig. 8) . The seedUngs were growing in very wet sand with the water 

 table only 8-10 cm. below the surface. On inspection the water table 

 zone proved to be very mucky and foul, and the effects on the tap- 

 roots seemed to be a rotting due to the action of micro-organisms, 

 with a proportionately increased development of laterals. 





\ 



a. 



Fig. 7 



Fig. 8 



Figs. 7, 8. — Primus pumila: fig. la, with stunted root system; i, horizontal layer 

 of matted willow roots in approximately natural position with relation to P. pumila 

 roots; fig. 8, root systems showing effects of high water table, Miller, Indiana: a, 

 Populus deltoides; b and c, Primus ptimila. 



Ammophila arenaria. — While this is the typical plant of the 

 open dunes, its seedlings are difficult to find, and its reproduction 

 is mostly vegetative through rhizomes. The spikes are thoroughly 

 exploited by insects, and when gathered late in the season very 

 few seeds will be found untouched. For this reason the seedlings 

 are very scanty, except in dense colonies where mature spikes 

 have been buried by fresh sand, and even then there are seldom over 

 6 seedlings from a whole spike. In the mature plant, as is well 

 known, there is a long slender rhizome producing usually 2 roots 



