342 THE CROWFOOT FAMILY 



Most of the crowfoot family ar(^ like iiuirsli-marigolds in 

 having their leaves petiolate. In some cases there is no 

 petiole. The leaf is then described as sessile,^ a term applied 

 to any stalkless organ of a kind which is commonly stalked. 



As regards their arrangement the leaves of marsh-mari- 

 golds are like almost all the others of the family in })eing 

 alternate, i. e., one at each node. In clematises there appear 

 two leaves at a node — such are called opposite — while in 

 anemonies there are often more than two forming a ring, 

 encircling the stem. Such a ring is termed a ivhorl or verticil,- 

 and the leaves are said to })e whorled or verticillote. When 

 leaves are opposite they are of course virtually in whorls of 

 two. - Leaves forming a rosette may approach closely the 

 verticillate arrangement, and it becomes a fair question 

 whether verticils may not be after all merely rosette-like 

 clusters in which the internodes have developed scarcely 

 at all. This view is favored by the fact that internodes of 

 perceptible length do sometimes separate the leaves of such 

 verticils as those of anemony. Furthermore, in clematises 

 the leaves before they expand often show one of a pair dis- 

 tinctly shorter (and therefore presumably younger) than 

 the other, just as if they were really alternate but with only 

 one of every two successive internodes developed. Although 

 we may admit that the alternate arrangement passes readily 

 into the verticillate even on the same plant, it is of course 

 necessary in practical description to distinguish the types. 



Students are sometimes puzzled as to how they may dis- 

 tinguish between a leafy shoot and a compound leaf, or be- 

 tween simple leaves and leaflets. They will be helped bj^ 

 remembering that a stem branch arises normally from the 

 axil of a leaf-member, and is an axis bearing leaves in the 

 axils of which buds may develop. Conversely leaf-members 

 normally subtend,^ i. e., stand just below, a bud or shoot, 

 and are lateral members radially disposed about an axis and 

 flattened, at least, when young, transversely with reference 



^ Ses'-sile < L. sessilis, sitting. 



' Ver'-ti-cil < L. verticillus, the whirl or whorl of a spindle, which is 

 a disk-like piece of wood or metal encircling it; hence, in botany a 

 ring of i)arts similar to one another encircling an axis. 



^ Sub-tend' < L. suh, under; tendcre, stretch. 



