222 THE BOOK OF NATURE STUDY 



number of fine lateral roots. If the younger roots of this kind be 

 compared with older ones the surface will be found to be at first 

 smooth, and later to become wrinkled transversely. This shows 

 that contraction has taken place, and these roots, in fact, serve to 

 pull the horizontal stem firmly down into the soil, and are of 

 subordinate use for obtaining food material. From the sides and 

 upper surface of the stem, however, roots of a different nature 

 spring. They are more slender, and bear numerous fine branches. 

 Their appearance shows them to be purely absorptive in contrast 

 to the fixing and contractile roots. 



At the end of the leafless region of the stem we find the tip 

 of the shoot turned somewhat upwards, and bearing the foliage- 

 leaves. Through the bases of these leaves a number of young 

 attaching roots project, and it is easy to realise how they correct 

 the upward curve of the tip and pull it down into the ground. To 

 either side of the terminal leafy shoot are smaller shoots, evidently 

 developed from lateral buds of last year, and similar lateral buds 

 may be seen farther back on the main shoot. Evidently this 

 grows on for a number of years, producing lateral shoots most 

 of which do not develop farther. 



The leaves of the Iris are very remarkable. Each has a large 

 sheathing base completely encircling the stem, and they succeed 

 one another closely on opposite sides of the stem, so that they 

 alternate in two ranks. The erect blade of the leaf is not, however, 

 flattened in the horizontal but in the vertical plane. It appears 

 as a pointed, sword-shaped outgrowth of the back of the leaf- 

 sheath, showing not an upper and lower surface, but two similar 

 flat sides. The veins run parallel in the leaf -blade. 



We can carefully remove the leaves one after another from the 

 shoot, and recognise how perfectly they enclose the summit of 

 this. Small lateral buds will be met with in the axils of the leaves. 

 Centrally the shoot terminates in a series of smaller and smaller 

 immature leaves overlapping one another, and ready to develop 

 into next year's foliage-leaves. The study of these with a lens will 

 show the origin and enlargement of the leaf-blade. 



When an inflorescence is not formed the shoot grows on year 

 after year. If, however, a plant bearing an inflorescence such as 

 that represented in the plate is examined the general features of 



