38 



BOTANICAL GAZETTE 



[JULY 



and a bud at each node. The bud frequently does not develop, 

 but the roots range widely under normal conditions through fresh 

 blown sand, often reaching a length of several meters. They are 

 thickly set with short laterals which bear abundant root hairs. 

 At times the tips of these roots are much enlarged for about lo cm., 

 gradually tapering in both directions and without branches. All 

 the roots are extremely wiry and tenacious, and on account of their 

 fineness and length cannot well be shown in a figure. 



It has generally been recognized ( Westgate 47) that A mmoph- 

 ila ordinarily requires annual supplies of fresh sand for its best 



development. Field ob- 

 servations in this region 

 would indicate also that it 

 does not thrive in sand 

 possessing an appreciable 

 amount of humus, and that 

 its colonies do not extend 

 across the border into such 

 a region (sand containing 

 humus). In at least one 

 case a colony seems to be 

 dying out in the presence 

 of a competing colony of 

 Calamovilfa, which has 

 not been studied closely, 

 but which seems to be 

 more humus tolerant than 

 Ammophila. Excavation 

 shows that the roots of mature plants of A mmophila exhibit little 

 response to organic material, following black layers only slightly and 

 frequently passing obliquely through them. A study of the seedlings 

 would seem to indicate that the extension of their roots may to some 

 extent be inhibited by the presence of decaying plant parts. In 

 fig. 9, a grew in pure sand, but in h all the roots came directly into 

 contact with buried Ammophila leaves and stems, and in c the 

 upper roots developed in pure sand and the lower in plant remains. 

 It will be noted that in b and c the roots do not extend beyond the 



Fig. 9. — Seedlings of AmmopMla arenaria, 

 2-3 months old : a, in homogeneous dune sand ; 

 b, all roots in contact with buried plant parts; c, 

 upper roots in sand, lower in contact with buried 

 plant parts. 



