iqiq] \VATER^fAX—ROOT SYSTEMS 41 



then away again, and showed in general no effect attributable to 

 the presence of the log. A marked attraction would have been 

 expected if the plant had been P. pumila. 



Cirsium Pitcheri. — ^This is apparently ecologically similar to 

 Artemisia caudata as to locality and general conditions of growth, 

 but it differs in having a strongly developed taproot with very few 

 and inconspicuous laterals. Occasionally, for no apparent reason, 

 a single lateral becomes prominent, as in Artemisia. 



Campanula rotundifolia. — This species is not uniformly dis- 

 tributed, but apparently germinates freely in restricted localities 

 on the open dunes, as well as in open places of a humus bearing 

 substratum. Its marked characteristic on the dunes is the long 

 taproot with U-shaped insertion of laterals (fig. 12a). In one case 

 where a buried marly layer was exposed on a slope a row 

 of seedlings was observed growing along the exposed edge of the 

 layer, and the roots were found to have grown horizontally inward 

 through the marly layer (fig. 126). They have not been observed 

 in contact with the dark layers, so their reaction to them cannot be 

 stated. 



Lithospermum Gmelini. — This is a fairly well distributed plant 

 on the open dunes, and is characterized by a very long, thick, black 

 taproot, with almost no laterals. A study of the structure might 

 reveal some interesting features as to the absorbing power of this 

 root. 



Lathyrus maritima. — This species is frequently the companion 

 of Ammophila, but it differs in root development in some important 

 respects. It germinates freely on the open dune, producing numer- 

 ous seedlings. No marked seedlings have been followed over 

 winter, but from the scarcity of 2-year-old plants they do not seem 

 to survive well, either on account of sand movement or possibly 

 because of lack of nutrition. The mature plant develops a wide 

 ranging rhizome, deeply placed and difficult to excavate unless 

 exposed in a blowout. The roots are scattered and usually not 

 over 10-20 cm. in length. Root tubercles are early developed 

 in dune sand (fig. 13), but less in some localities than in others, 

 possibly on account of unequal distribution of infecting organisms. 

 When present the tubercles occur only near the surface of the sand. 



