24 



BOTANY 



PART I 



(Fig. 24) or of the Jerusalem Artichoke (Helianthus tuberosus) are also 

 subterranean shoots with swollen axes and reduced leaves. They 

 are formed from the ends of branched, underground shoots or runners 

 (stolons) and thus develop at a little distance from the parent plant. 

 The so-called eyes on the outside of a potato, from which the next 

 year's growth arises, are in reality axillary buds, but the scales which 

 represent their subtending leaves can only be distinguished on very 

 young tubers. The parent plant dies after the formation of the tubers, 

 and the reserve food stored in the tubers nourishes the young plants 

 which afterwards develop from the eyes. As, in their uncultivated 



Pia. 24.— Part of a growing Potato plant, Solanum tuberosum. The whole plant lias been de- 

 veloped from the dark-coloured tuber in the centre. (From Nature, copied from one of 

 Baillon's illustrations, ^ nat. size.) 



state, the tubers of the Potato plant remain in the ground and give 

 rise to a large number of new plants, it is of great advantage to the 

 new generation that the tubers are produced at the ends of runners, 

 and are thus separated from one another. Similar advantages accrue 

 from surface runners, such as are produced on Strawberry plants. 

 Surface runners also bear scale-like leaves with axillary buds, while 

 roots are developed from the nodes. The new plantlets, which arise 

 from the axillary buds, ultimately form independent plants by the 

 death of the intervening portions of the runners. 



Still more marked is the modification experienced by shoots which 

 only develop reduced leaves, but the axes of which become flat and 

 leaf-like, and assume the functions of leaves. Such leaf-like shoots are 

 called cladodes or phylloclades. Instructive examples of such forma- 



