Cii. IV, 11] SPECIAL FUNCTIONS OF STEMS 



191 



Fig. 134. — Solomon's Seal, Polygonatum 

 multijlorwm; X f . Each -seal" niark.s a fallen 

 shoot, and a year's growth of the rootstock. 

 (From Strasburger.) 



11. The Form.s and Functions of Stems not Connected 

 WITH Support of Foliage 



As with other 

 plant parts, stems 

 are not hmited to 

 the one primary 

 function in adapta- 

 tion to which they 

 seem clearly to have 

 been evolved, but 

 perform also others, 

 which sometimes re- 

 place the original 

 function. Thus are 



produced new organs, with distinctive aspect and structure. 

 The mo.st frequent additional function of stems is storage 

 of food or water. All woody stems store 

 food over winter, but since ample room 

 therefor exists in the ordinarj^ tissues, — ■ 

 in pith, bark, meduUarj^ rays, and parts of 

 the fibro-vascular bundles, — such stems 

 exhibit no external evidence of the storage 

 function. Some stems, however, do show 

 marked swellings resulting from storage of 

 food and water, as especially clear in the 

 pseudobulbs of epiphytic Orchids (Fig. 

 126). Storage of food is commonest in 

 underground stems or rootstocks, which 

 thereby are given a swollen aspect, as for 

 example in Solomon's Seal (Fig. 134), 

 where a new piece of food-filled stem, 

 ^ ,^^ ,, producing a new shoot, is made each year. 



Fig. 1.35. — Atyp- ^^ '^ <■ i • t • 



ioai corm, composed Similar arrangements are found m Iris, 



mostly of stem, of 'pt-juj^j^ ^ud others, and reaches an ex- 

 Crocus. (From . ' ' 

 Figurier.) tremc in the CORM of Crocus (lig. 135), 



