290 The Ohio Naturalist. [Vol. II, No. 8, 



ROSETTE PLANTS OF OHIO. 



Frederick J. Tvlkr. 



Among the many forms of vegetation represented in Ohio, the 

 rosette is not the least interesting and remarkable. There are 

 about 155 species and varieties of plants in the State which ex- 

 hibit this habit during some period of their life history and since 

 many of them are very abundant and some are classed as bad 

 weeds, they form a conspicuous and important part of the flora. 



Rosette plants are characterized by a basal tuft or whorl of 

 leaves which may be persistent ( perpetual rosettes, as the com- 

 mon Dandelion) or may disappear as the plant reaches maturity 

 (temporary rosettes, as the Mulleins and most other rosette- 

 biennials). This basal tuft of leaves is due to a shortening 

 (non-development ) of the interuodes of the stem, thus bringing 

 the leaves close together. The amount of stem reduction may 

 be approximated by counting the number of leaves in a rosette 

 and comparing with the number of leaves on a flowering stem of 

 the same plant. The stem forming the central axis of the rosette 

 of Onagra biennis, the common Evening Primrose, will be found 

 to bear 50 to 70 times as many leaves as the .same space of flow- 

 ering stem. In other words a stem length of 13 to 17 in. has been 

 shortened to )/( in. 



The advantage of the rosette habit is chiefly in the protection 

 which it affords from extremes of temperature and from drying 

 winds, browsing animals, etc. The typical rosette rarely projects 

 more than an inch or so above the ground and the leaves are usually 

 spread out flat upon the surface. In Winter the rosette is well 

 protected by even a light blanket of .snow and is often partially 

 covered by the debris of higher vegetation which has been cut 

 down b}^ frost. 



In this latitude the majority of rosette plants are biennials, 

 that is, plants which complete their life cycle in two years, 

 spending the first year in getting a foothold, tstablishing a strong 

 root system, and usually in storing up some reserve food material. 

 The next year they start out vigorously on their lifework of pro- 

 ducing seed. It is easily seen that the ro.sette habit is peculiarly 

 adapted to the needs of a biennial during its first year's growth. 

 It is compact, well protected for the Winter and the preservation 

 of reserve food material is made ea.sy. But for the all important 

 work of the second year the rosette is not at all adapted. Now 

 it is too compact, only a limited amoinit of foliage can be borne 

 by the short stem, and not enough space can be given to the pro- 

 duction of flowers and fruit. So the biennial abandons the rosette 

 habit at the beginning of the second growing sea.son and grows 

 up into a tall, branching herb. Familiar examples are the Turnip, 



