Jan., 1905.] 



Plants with Nodding Tips. 



267 



PLANTS WITH NODDING TIPS. 



John H. Schaffner. 



In the plant kingdom are to be found many peculiar adapta- 

 tions. One of the most interesting is the habit which some 

 species have of keeping the growing tip curved downward during 

 the period of development or until the stem has attained its 



growth for the season. This 

 curving of the tip of the stem 

 appears much like the arch 

 commonly developed in 

 sprouting seedlings but must 

 be for a different purpose. 



The nodding of the grow- 

 ing tip is strikingly seen in 

 such plants as Solidgo can- 

 adensis (Fig. 1) and Asimina 

 triloba. Some species of a 

 genus mav nod while others 

 show no sign of a curve in 

 the stem tip. Thus Gaura 

 parviflora nods very strongly 

 while Gaura biennis, it ap- 

 pears, does not nod at all. In 

 most cases the curve is quite 

 rigid but in some the nodding 

 is merely the result of the 

 flexibility of the stem. A 

 few species have the tips nod 

 at night but become nearly 

 straight in the daytime. Whatever the cause or factor which 

 induces plants to nod, there is probably no doubt but that the 

 habit is a means of protection to the delicate terminal bud. 



Fig. 1 

 ding tips. 



Solidago canadensis showing nod- 



Species with Rigid Nodding Tips. 



Salix cordata Muhl. 

 Ulmus americana L. 

 Ulmus fulva Mx. 

 Asimina triloba (L.) Dun 

 Albizzia julibrissin Boiv. 

 Vitis labrusca L. 



Vitis vulpina L. 

 Ampelopsis cordata Mx. 

 Parthenocissus tricuspidata(S.& Z.)P]. 

 Gaura parviflora Dougl. 

 Solidago canadensis L. 



Erigeron philadelphicus L. 



Species ivith Flexible Tips. 

 Tsuga canadensis (L ) Carr. Juniperus communis L. 



Species with Tips which Nod at Night. 

 Cassia cham;ccrista L. Euphorbia nutans Lag. 



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