10. THE SHOOT. 



25 



similar trees, and are the only parts of the tree which produce flowers 

 and fruit : they are the fruit-spurs. 



The Bulb and the Corm are examples of shoots with short stems ; they 

 are, in fact, forms of the bud produced underground. 



The Bulb consist of a flattened discoid stem, bearing a number of scaly 

 leaves closely arranged on its upper surface, and roots on the lower sur- 

 face. The leaves may either invest each other, as in the Onion, when the 

 bulb is said to be tunicate (Fig. 13 B) ; or they may only overlap at their 

 edges, as in the Lily, when the bulb is said to be imbricate. 



Aerial buds develope in some plants into small bulbs, termed bulbils, as 

 in Lilium bulbiferum, Denlaria bulbifera, and in some species of Onion. 



The Corm consists of a rounded or flattened stem which occupies a rela- 

 tively larger proportion of space than that of the bulb, and is invested by 

 only a few scaly leaves. It occurs in Crocus and other Iridese. 



The Tuber is a dwarf -shoot, consisting of a swollen stem bearing small, 



Fi&. 14. A Rhizome, with unlimited growth, of Oxalis Acetosella (wood-sorrel) ; n scales ; 

 I foliage-leaves ; V remains of older foliage-leaves ; bl flower ; 7i bracts. B Rhizome with 

 limited growth of Potygonatum officinale (Solomon's Seal) ; I scar of last year's herbaceous 

 aerial shoot; II aerial shoot of this year, which is the anterior portion of the shoot 2 ; III 

 bud of next year's herbaceous aerial shoot, which is the continuation of the shoot 3 ; 

 n, scales ; b and b' leaves from the axils of which the shoots 2 and 3 have arisen ; w roots. 



scaly leaves ; it is usually developed underground, as in the Potato and 

 and the Jerusalem Artichoke (Helianthus tuberosus, Fig. 13 A). 



The morphological nature of the tuber is readily demonstrated by un- 

 covering the underground shoots of a Potato-plant, when they develope 

 into ordinary foliage-shoots. Again, if the development of tubers be pre- 

 vented by cutting off the underground shoots, the buds in the axils of the 

 leaves above the ground develope into tubers. 



The Flower is another form of dwarf-shoot, the leaves of which, when 

 present, are arranged closely together. The morphology of the flower is 

 discussed in subsequent paragraphs. 



