Ch. IV, 11] SPECIAL FUNCTIONS OF STEMS 



191 



Fig. 134. — Solomon's Seal, Polygonatum 

 X f. Each "seal" marks a fallen 

 year's growth of the rootstock. 

 (From Strasburger.) 



11. The Forms and Functions of Stems not Connected 

 with Support of Foliage 



As with other 

 plant parts, stems 

 are not limited to 

 the one primary 

 function in adapta- 

 tion to which they 

 seem clearly to have 

 been evolved, but 

 perform also others, 

 which sometimes re- multiflorum 



. . . • • i shoot, and 



place the original 



function. Thus are 



produced new organs, with distinctive aspect and structure. 

 The most 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 ordinary tissues, — 

 in pith, bark, medullary 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. 

 Similar arrangements are found in Iris, 

 Trillium, and others, and reaches an ex- 

 treme in the cOrm of Crocus (Fig. 135), 



Fio. 1.35. — Atyp- 

 ical oorm, composed 

 ■kOtUy of stem, of 

 Crocus. (From 

 Figurier.) 



