I 



287 



to the liexamerous which exists between tetramerous and pcnta- 

 merous or hexamerous species in many other genera of plants, 

 assigns to the famiUar northern species the following names: 



•^ Unifolium Ca^ ABENSE— Mazarii/iemum Canadense, Desf 

 *^Unifolium ^\YO\A\^yi—Convallariabifolia, Linn, 

 ^ Unifolium l:'^\YO\A^51A~Convallaria trifolia, Linn. 

 ^ Unifolium STELLATUM— <r^;/z;^//^zr/^ stellata, Linn. 



' Unifolium sessilifolium — Smilacina sessilifolia, Nutt 

 *^ Unifolium amplexicaule — Smilacina amplexicaidis, Nutt. 



The name Unifoliii^n seems as if it should indicate one-leaved 

 plants, but there is no species of the genus which has strictly that 

 character. The very type is two-leaved, and the other species 

 bear three or more leaves to every stalk. Whence, then, this 

 name ? Dillen, who is but one of a long line of authors who 

 adopted it, informs us* that it was suggested by the solitary leaf 

 which, in the original species, comes up from the rootstock apart 

 l^om the two-leaved proper stem. None of the many-leaved 

 species display any such separate solitary leaf; but that failure 



West 



ifolium 



nve to nine instead of the usual three, can require a new and 

 niore strictly applicable name in the place of Trifolium, 



On the Opening of Stomata. 



It is a well-known fact that the stomata on the leaves and 

 other organs of plants are found open at one time and closed at 

 another ; that they are open ordinarily when the plant is wet, 

 closed when its moisture is largely withdrawn ; and that the 

 property of opening and closing is lost with the activity of the 

 guard-cells. 



Various hypotheses have been called in to explain the causes, 

 as well as the manner, of this opening and closing. The one 

 generally admitted at the present day is that of Schwendener.t 



*Nova Plantarum Genera, p. 13S. 



f Uel)er Ban und Mechanic dcr SpaltoefTuungen. Monatsberichte der Acad- 

 emic dei- Wissenschaftcn zu Eerlin, 1881, p. S83. 



