Dec, 1900] Tyler — Geophilous Plants. 21 



GEOPHILOUS PLANTS OF OHIO. 



F. J. Tylee. 



Geophilous — meaning earth loving— is a term which has recently- 

 been applied to such plants as have some special adaption, which 

 enables them to withdraw beneath the surface of the ground when 

 adverse conditions, such as extreme heat and drouth, cold, etc.^ 

 overtake them. Such adaptions may be classified as 



Rhizomes, 



Bulbs, 



Corms, 



Crowns. 

 Rhizomes are underground stems and like other stems may be 

 simple or branched. The branched rhizome is, however, the most 

 common form since it combines vegetative reproduction with the 

 other advantages of a rhizome habit. The Brake Fern (Pteris aqui- 

 lina L.) is an example of a much branched rhizome and Solomon's 

 Seal (Polygonatum biflorum Ell.) of a nearly simple rhizome. 



The stem of a rhizomatous plant may remain permanently 

 underground, as is the case with all ferns except the tree ferns of the 

 tropics. An annual stem is, however, usually sent to the surface 

 and this may be a lateral branch from the main subterranean stem 

 or it may be a continuation of the rhizome, in wliich case the next 

 year's rhizome will be a lateral branch and thus the whole rhizome 

 will be made up of a number of distinct segments. Various members 

 of the Iris group are good examples of this. In at least one genus of 

 Ohio plants— Smilax— there are some members having both a per- 

 ennial woody stem and a well developed rhizome. It may be that 

 these plants are leaving the rhizome habit and are taking up the 

 woody stem liabit. 



Perliaps in most cases rhizome plants became such through the 

 gradual covering of trailing stems. It is a protection and a saving- 

 of building material to a plant if its stems are trailing or creeping, 

 still more so if they are covered by leaf mould or soil. If rhizome 

 plants were once trailers there should be every gradation between 

 the two and so we find. The Trailing Wahoo is a good example of 

 this, since some of its stems are often covered by leaf mould or soil 

 while others are on the surface or some inches above. Many of the 

 Ericaceae are in this transition stage between trailers and geophytes. 

 The Wintergreen (Gaultheria procumbens L.) has a long, creeping 

 stem which is often or usually covered by leaf mould. It roots 

 freely and sends up perennial woody branches to the surface. It is 

 hard to say in such cases whether the plant is geophilous or not. 



