122 STEM-TUBERS [CH. 



e.g. Couch-grass and the slender creeping rhizomes of 

 Garex arenana and Psamma arenaria, the sand-bindiug 

 Sedge and Grass so much used in reclaiming land on the 

 sea-coast. 



The student will see that just as with creeping stems 

 above ground, so with rhizomes below, every stage is to 

 be met with between annual and perennial outgrowths 

 which remain attached all their lives to the parent centre, 

 to such as become very early detached as independent 

 terminal (or axillary) buds with a store of reserve 

 materials, and the understanding of this facilitates our 

 comprehension of the next category of underground shoots, 

 viz. Stem-tubers. 



In the Potato-plant, it only requires little more than 

 casual observation to see that each tuber (potato) is 

 attached by its posterior end to an underground stolon 

 springing from the axil of one of the lower leaves, and that 

 any assumed resemblance of this stolon to a root results 

 from lack of attention ; for although it is thin, long, 

 cylindrical, and devoid of green colour, it is also provided 

 with nodes and scale-leaves along its course, and ends in the 

 tuber. More careful observation of a Potato-plant dug up 

 in July shows that the tuber is nothing but a swollen bud, 

 with scale-leaves of its own : as it grows bigger during the 

 period towards the end of summer when the small potatoes 

 are being filled with starchy materials from the leaves, 

 these small leaves and the minute buds in their axils 

 become driven further and further apart on the enlarging 

 periphery of the tuber, as the stores of reserves swell the 

 stem of the bud : it is these minute scales and their still 

 smaller axillary buds which are popularly termed the 

 " eyes " of the potato. These points are made out even 

 more clearly on "seed-potatoes" in spring, because the buds 

 ("eyes") are then beginning to sprout. 



