PARASITES AND WALL PLANTS. 151 



dispute its place among wall plants, for it can grow 

 in the driest chink of any wall or terrace. I have 

 seen this shrub not only grow, but even flower and 

 fruit on the stem of a Palm tree at some distance 

 from the ground ; behaving in fact after the manner 

 of an epiphyte or air plant : for I suppose that it was 

 not acting as a parasite. This Xicotiana grows freely 

 from seed. If it appears on a terrace, or in the crevice 

 of any decorative work, it is best to pull it up at once, 

 as it will do mischief by forcing away the plaster. 

 The long narrow flowers are ornamental, and the 

 capsule, as might be expected, differs little from that 

 of the Tobacco. 



Two little linear-leaved plants of the Composite 

 order, and belonging to the genus Conyza (or 

 Phagnalon) may be found clinging to almost every 

 old wall. The one, C. saxatilis, has trim little bronze 

 thistle heads on long stalks ; the other C. sordida, has 

 smaller and more numerous flower tops. 



Another common wall plant is Theligonum, with 

 its inconspicuous greenish strap-shaped flowers. This 

 watery herb will thrive in any shady corner, but the 

 most likely place to find it is on some old masonry 

 with north exposure. The allied pellitory (Parietaria) 

 is gathered here to make a tisane ; the stalks only are 

 used, the leaves being carefully removed. Cotyledon 

 abounds, and various species of Sedum. 



Ceterach (Fig. 59) and Maiden Hair (Adiantum) 

 complete the list of what may be called the regular 

 Wall Plants. The former is a pinnate lobed fern, 

 covered beneath with reddish brown scales. This plant 

 is able to endure the sun ; but the Maiden Hair re- 

 quires both shade and moisture. It grows in wells and 



