365 



VEGETATION OF DRYING MUD AND RETARDED 

 GERMINATION. 



J. SALISBURY, D.SC, F.L.S. 



[Con^mtied from page JJ2). 



In the present season six samples of mud were taken from 

 the Welsh Harp from a depth of 3 to 6 inches, after the top 

 3 inches of exposed mud had been removed. Any seeds 

 present may, therefore, be assumed to be several years old 

 at least. Three samples were moistened and placed under 

 conditions favourable to germination, whilst the remaining 

 three were first sun-dried. In all three of the latter seedlings 

 appeared, whilst none appeared in the three former ; when 

 these in turn had been sun-dried and remoistened, however, 

 two samples exhibited seedlings. Unfortunately, during the 

 writer's absence, all the seedlings died, so that their identity 

 is unknown. The results, however, demonstrate the presence 

 in the mud of dormant seeds, perhaps of considerable age, 

 and the stimulating effect of dessication. 



In exartiining the vegetation of the exposed mud the de- 

 velopment of aerenchyma was noted in many individuals, the 

 species involved being Bidens cermia, B. tripartita, Epilobium 

 hirsutiim, Lycopus eiiropaeus and Scutellaria galericulata. 



A very interesting distribution of hairs was noted for 

 Polygonum nodosum v. salicifolium growing amongst other 

 plants, chiefly Malachium aquatitum. The leaves produced 

 in the shelter of the surrounding vegetation were densely 

 hairy beneath, whilst those in the less humid air above were 

 only sparsely hairy. Moreover, some of them which were 

 partly sheltered and partly exposed exhibited the same 

 distinction between the respective parts. The condition was 

 thus the very reverse of that exhibited by Ulmaria palustris 

 (c.f. R. H. Yapp, Ann. Bot., pp. 815-870, 1912.) 



