ON WALLS, ROCKS AND STONY PLACES 323 



flowers, which are in small, terminal, three-cleft panicles, have very 

 short, blunt sepals ; and much longer, narrow, pointed petals. 



The same order {Crassidaceoe) includes the House Leek {Semper- 

 vivum tectorum) — a plant 

 which has been introduced 

 into Britain, and is now com- 

 monly seen growing wild on 

 rocks and on the roofs of 

 country houses. Its spread- 

 ing offsets give rise to globular 

 tufts of flowerless shoots, 

 and to thick, succulent, 

 flowering stems that grow to 

 a foot or more in height. The 

 lower leaves are ovate, acute, 

 thick, flesh}'^, edged \dt\\ red, 

 and arranged in a dense 

 rosette ; and the flowering 

 stem, with its sessile leaves, 

 is covered with a short, sticky 

 down. The flowers are of a 

 dull pink or purple colour, and 

 are sessile along the spread- 

 ing branches of the stem. 

 They have usually about 

 twelve short sepals ; the same 

 number of pointed petals, 

 two or three times the length 

 of the sepals ; about twice as 

 many stamens ; and an ovary 

 of as many carpels as there 

 are petals and sepals. It is 

 interesting to note that half 

 the stamens — those forming 

 the inner whorl — produce no 

 pollen, and that their anthers 

 are often modified into ovaries, the ovules of which, however, do 

 not mature. This plant flowers in July and August. 



Oiu- last selection from this order is the Wall Pennywort or 

 Navel wort {Cotyledon umbilicus) — a peculiar plant, common on 

 rocks and walls in the South and West of England. It has a hard 



Y 2 



THE London Pride or St. Patrick's 

 Cabbage. 



