io6 THE VEGETATIVE ORGANS 



in the Ribwort. Note the differences in the length of the 

 leaf-stalk and the size of the blade from the lower and outer 

 to the upper and inner part of the rosette, and observe how 

 this prevents much overshadowing in spite of the crowding. 

 Leaves springing from the stem near the ground in this 

 manner are called radical leaves to distinguish them from 

 leaves rising, like those of a Stock, on a taller stem above 

 ground and known as cauline leaves. The habit of forming 

 rosettes is very common in plants growing on mountains, 

 and on rocks where the soil is liable to dry up at certain 

 seasons. But rosette-formers are not uncommon in other 

 habitats, especially in grassy swards. As the buds which 

 arise in the leaf-axils of such plants also tend to form rosettes 

 close to the parent, a large cushion is in time produced. 

 Short lateral shoots of this kind are called offsets, and they 

 serve as an important means of vegetative reproduction 

 (Figs. 64 and 257). 



If opportunity offers, it will be interesting to study the 

 various rosettes of the plants growing on a rockery. You 

 will find many forms, some compact, others lax. There 

 will be varying lengths of offsets, and varying forms and 

 sizes of cushions. Fleshy leaves in all grades may be found, 

 some, like those of the Houseleek, very thick indeed and 

 able to store much water for use in times of drought. 



Observations on opening buds. If you place winter shoots 

 of trees in water for a few weeks you will be able to watch 

 the opening of the buds, and it is easy to study the more 

 important details of their structure. In such opening buds 

 observe : (1) the number and arrangement of bud-scales ; 

 (2) their origin from leaves, leaf-bases, or stipules ; (3) the 

 transition from bud-scales to foliage-leaves ; (4) the 

 arrangement and manner of folding of the foliage-leaves ; 



(5) whether the leaf-stalk or blade is first developed ; 



(6) the behaviour of the leaves as they expand ; (7) the 

 differences between leaf-buds and those containing flowers. 



