n6 THE YOUNG NATURALIST. 



known, or a more universal favourite. Scarcely a cottage garden is 

 to be seen without its plants of wall-flower, the delicious fragrance of 

 which scents the air in the balmy spring mornings and evenings of 

 April and May. By gardeners the wall-flower is generally treated as 

 a biennial, the seeds are sown in early summer, the young plants being 

 pricked out when large enough to handle, then in late autumn planted 

 out where they are to bloom in spring, and when done flowering they 

 are pulled up and destroyed. If allowed to remain they are usually 

 killed the succeeding winter if the frosts are at all severe. Yet under 

 favourable conditions it will grow and form a large shrubby bush with 

 a woody rootstock, and increasing annually in size. Although now 

 thoroughly naturalised, the wall-flower is not a native of this country, 

 having been introduced from Spain, and its original home is on the 

 rocky shore of the Mediterreanean. So that to be seen in its full 

 natural and unaffected beauty it must be viewed adorning craggy 

 precipices or old ruins, where it finds a congenial habitat, and clothes 

 with its grateful loveliness the evidences of man's mouldering handi- 

 work. The famous ruins of Melrose Abbey to wit, have an added 

 charm in the gorgeous colouring of the bright yellow wall-flower, 

 which in great profusion covers the inaccessible walls and roofs in 

 early summer. It seems to revel in the driest situations, the plants 

 growing in the crevices of the wall becoming hard, gnarled, stunted 

 specimens, yet flowering and seeding freely, the dry root-hold prevent- 

 ing them suffering from the winter frost, their greatest enemy, and 

 inducing a slower growth and hardier constitution. It is the rapid 

 luxuriance in rich soil which enfeebles it, so as to make it ready prey 

 to climatic changes. It flourishes freely as far north as the ruins of 

 Kinloss Abbey, on the shores of the Moray Frith. 



The wall-flower is a typical representative of the large and well- 

 defined natural order Crucifer<z, which receives its name and is dis- 

 tinguished by, the cruciate or cross-shaped blossoms. Let us 

 examine a bloom of the common wall-flower. We observe first four 

 green sepals, one pair a trifle larger than the other, and slightly en- 

 larged or swollen at the base. These are easily removed, when the 

 four petals are seen to have rather a long stalk or claw, which gives 

 the corolla a tubular shape, the flat expanded portion or limb spread- 

 ing outwards crosswise x These, too, can be readily detached, leav- 

 ing the stamens exposed, they are six in number, arranged in two 

 opposite pairs of equal length, with a solitary shorter one between each 

 pair ; this arrangement is called tetradynamous, and is one of the 

 botanically characteristic features of the cruciferous flowers. As the 



