1861.] KENTISH BOTANY. 239 



At Walmer^ or rather on Walmer's shingly beach, on the west 

 end of the village, towards Kingsdown, there were observed 

 several very luxuriant forms of Medicago denticulata ; the stems 

 were quite procumbent, above a foot long, bushy, or with nume- 

 rous series of branches, and with only a single twist, or a turn 

 and a half, of the coclileate spiral fruit. 



During the subsequent portion of our walk we observed other 

 gigantic forms of Leguminiferous plants, and these will be men- 

 tioned in the sequel. 



Medicago denticulata was probably long considered only a 

 variety of M. maculata on the one hand, and M. minima on the 

 other. It differs from the former in the absence of a spot on 

 each leaflet, and it is usually smaller in size. From the latter it 

 differs in its flatter fruit. The fructification of M. maculata 

 resembles in figure the nave of a cartwheel, having many convo- 

 lutions of the spiral. In M. denticulata the convolutions are 

 few , viz. from one to three, with flat sides ; in M. macidata 

 and M. minima, the convolutions are numerous, and the base 

 and apex of the cochleate spiral are rounded, not flat. Also when 

 the fruit of M. denticulata is quite ripe, it is furnished with pro- 

 minent radiating ribs, and it is also of a black colour. 



This Medick, M. denticulata, has been observed and collected 

 during recent years at Wandsworth, near the steamboat- pier ; 

 also at Southampton, not far from Jtchin Ferry, and at Black- 

 situations for themselfes ; or selected bi-ick walls and tiled roofs because there was 

 no natural site present suited to their economy. 



Some plants have a preference for walls and roofs in this part of the kingdom, 

 but are not exclusively restricted to such places. Saxifraga tridactylltes and 

 Sedum acre are examples. These indeed often grow on waUs, but in some places 

 they grow plentifully on the ground. Various species thrive equally both on walls 

 and on the ground. Shepherd's-purse {Capsella Bursa-pastoris) and Arenaria 

 serpylUfoUa or A. leptoclados are familiar examples. Parietaria officinalis, 

 liiuaria Cymhalaria, Centrantlius ruber, and Cheiranthus Cheiri rarely grow on 

 any other situation but on walls. The first of the last-mentioned fom' plants is 

 universally admitted to be a genuine native ; the three remaining are as univer- 

 sally branded as certainly introduced, their introduction being at a more or less 

 remote period. 



These three species, viz. Linaria, Cheiranthus, and Centranthus, grow in the 

 southern parts of oiu* isle 011 lualls, because' here there are but few places where 

 rocks of any kind crop out or rise above the surface of the ground. Rocks there 

 are none in the south-east of England, except a few in Sussex, and where the 

 chalk, the common substratum of a thu'd part of England, is laid bare by the sea, 

 or by the operations of the quarrymen. Hence but little stress can be laid on tlie 



