Fnr Aujiiist. 1922 



225 



Plants With Subterranean Stems 



FLORUM AMATOR 



WIIA'I' is ;i plant stem? it is tliu axis of tlic plant 

 on wliich all other ort^ans of the ])lant are borne. 

 I tranches are secondary stems, that is stems grow- 

 ing- out of the main stem. Stems at the very beginning 

 produce roots. The stem is an ascending axis, except 

 those subterranean stems which are in the form of a 

 rhizome, and the root is the descending axis. 



There are two general classes of stems, namely, alcove- 

 ground and subterranean or underground stems. The 

 pronounced characteristic of above-ground stems is that 

 they bear leaves. Underground stems do not bear true 

 leaves, but the rudiments of leaves or what answers to the 

 leaves of above-ground stems. 



Abovc-Gronnd Stems. — These stems are of several dif- 

 ferent forms, which are usuallv classified as follows : 

 Herbaceous stems which die down to the ground each 

 season after flowering; siiffrutesceiif. wdiich are slightly 

 woody below, but herbaceous above ; fntticose, woody and 

 living through the years, but growing however not more 

 than four times a man's height ; arborescent, in appearance 

 and manner of growth tree-like, and in size ajiproaching a 

 tree; arboreous, forming a proper tree trunk. These dif- 

 ferent forms of above-ground stems are found everywhere 

 and ma\' be readily observed, but subterranean or under- 

 ground stems are not easily observed, and few conse- 

 quently have any knowledge of these. It is of these, 

 therefore, we purpose to speak. 



Subterranean or Underi^round Stems. — "These," says 

 the late Prof. Asa Gray in his excellent botany, "are very 

 numerous and various, but they are commonly overlooked 

 or else are confounded with roots. From their situation 

 they are out of ordinar\- sight : but they will well repay 

 e.xamination, for the vegetation that is carried on under- 

 ground is liardlv less varied <ir important than that above 

 ground." 



Subterranean stems arc of four different kinds, namely, 

 the Rhizoma, Rhizome or Rootstock ; the Tuber; the 

 Corni, or solid bulb, and the true bulb. 



Rhicoines, or Rootstoeks. — The Rhizome or Rootstock 

 is a creeping stem or branch growing partly or wholly l)e- 

 neath the soil. These are variously spoken of as scaly, 

 running or creeping roots. The Spearmint, Mentha vcri- 

 dis. the Peppermint, Mentha f^iperita, the taste and fra- 

 grance of wdiich are so refreshing, and also the hated 

 "Couch Grass" or "Quick" Grass, Agropyron repens. are 

 common and therefore well-known examples of plants with 

 rhizomes. Acorns cahriiins Calamus, or Sweet Flag, is 

 another example of a plant whose stem is a rhizome. The 

 rhizome of this is sold by druggists under the commercial 

 name. Calamus ; it is edible and is often made more palat- 

 able by a coating of sugar and thus becomes a confection. 

 The tender young spadices and the tender bases of the 

 sword-like leaves also of xAcorus calamus are edible. Still 

 other examples of well-known plants with rhizomes are 

 Polygoiiatniu bidoruni and Polygonatum gigantcuni, the 

 smaller and the greater Solomon's Seal ; Smilicina race- 

 inosa. False Spikenard ; Iris versicolor and Iris prismatica, 

 the Larger and the Slender Blue Flag, often called Iris 

 and Fleur-de-Lis. These plants which have been men- 

 tioned as having rhizomes are all either indigenous or 

 naturalized, but some cultivated Irises have rhizomes. 



Tubers. — -\ tuber is a part of a rhizome (rootstock) 

 more or less thickened and with buds ( eyes) on its sides. 

 As a matter of course there are all gradations between a 



ri;((lslock and a Inlier. The connnon potato — Solanum 

 tuberosum — and the Jerusalem Artichoke — Helianthus 

 tuberosus — are well-known typical examples of the tuber. 

 Other examples of the tuber are the Dahlia — Dahlia Taria- 

 blis; the turnip — Hrassica and the Ground-Nut or Wild 

 P>ean — .Ipios tulyeinsa. All of these tubers, which have 

 been mentioned, are edible. The scalelike growth, which 

 is seen at intervals on rhizomes and the eyes which are 

 seen on both rhizomes and tubers correspond respectively 

 to the leaves which are seen on the above-ground stems 

 and the buds seen in the axils of these stems. 



I he Corni or Solid Bulb. — A corm is a thick and ex- 

 tremely short and fleshy underground stem, not unfre- 

 quently of greater breadth than height. From the upper 

 end of the corm arise stalks and leaves and from the 

 lower the roots descend or spread out. .Among cultivated 

 plants, the Crocus, Gladiolus and Cyclamen are well known 

 examples of plants growing up from corms, and the 

 Indian Turnip^ — ArisavnO' triphyllum — among wild plants. 

 The first two and the last are reproduced annually, the 

 new corms forming on the sides and summit of the old, 

 but the corms of the cyclamen enlarge and go on produc- 

 ing leaves and flowers through the years. A corm re- 

 sembles a tuber in its habit of budding on its sides, that is 

 from the axils of its leaves but these leaves are not scales 

 as in the case of rhizomes and tubers but are the bases 

 of the foliage leaves which cover the surface of the corm. 

 The corm resembles the true bulb in having these sheathes 

 or wide scales, but the solid part of the stem makes up 

 most of the bulk which is not the case in the true bulb. 



The Bulb. — A bidb is an underground stem whose solid 

 centre is like a reduced corm, but whose major part is 

 made u\i of thickened scales which are leaves or the bases 

 of leaves and which cover the central corm-like part. In 

 fact a bulb is a bud on an extremely short stem and sur- 

 rounded with fleshy scales. In the bases of these thick, 

 fleshy, overlapping scales is stored the food for the most 

 ])art for the future growth of the central corm-like bud, 

 surrounded by these scales but in the case of rhizomes, 

 tubers, and corms the store of food for future use is in 

 these subterranean stems. In lilies we see examples of 

 bulbs with thick narrow scales. 



In Hyacinths and Onions we have examples of coated 

 or truncated bulbs, that is bulbs whose scales enwrap 

 each other in concentric layers. The small bulbs which 

 grow out of the large ones underground or in some cases 

 above ground in the axils of the leaves are called bulblets. 

 The bulblets which grow in the axils of the leaves of some 

 kinds of Lilies or in the flower clusters of the Onions 

 never grow into branches since they are buds with thick- 

 ened scales, but when mature, dro]) to the ground and 

 take root there and form new plants. 



A proper and effective method of studying underground 

 or subterranean stems is to procure a rhizome, for ex- 

 ample, of an Iris, a tuber of a potato, a corm of a 

 Cyclamen and a Gladiolus, a bulb of a Lily and a Hyacinth, 

 and note first their forms ; secondly their bud scales, and 

 buds; thirdly their true roots, and from what point these 

 roots spring, and from what point the new plant grows 

 annually. 



We will readily understand the importance of under- 

 ground stems upon considering the fact that the majority 

 of our most used edible vegetables and many of our beauti- 

 ful flowering ]ilants have stems which are wholly or partly 

 subterranean. 



