THE VEGETATIVE ORGANS COMPARED 341 



(Fig. 291). The relation of the very narrow mouse-tail leaf 

 to one of the marsh-marigokl type may be understood Ijy 

 supposing the nerves to be reduced to a single rib. A leaf 

 in which the framework consists of only one or two ribs, 

 may be termed costate} The simple leaf of the silky clematis 

 may be likened to a less narrowed marsh-marigold leaf in 

 which, however, the ribs are reduced to one midrib from 

 which veins are given ofT on either side. Or, better, we may 



Fig. 296. — Staminodes. .4, Anemone Pulsatilla. B, Ranunculus acris, view 

 from above. C, same, cut vertically; the shaded area (S) indicating the 

 surface secreting nectar. D, Nigclla damescena, view from above. 

 E, same, cut vertically; secreting surfaces (S) shown as before. All 

 variously enlarged. (Redrawn from Prantl.) 



Fig. 297. — Ovary of an anemony, opened to show the two pairs of rudi- 

 mentary o\'ules above the single normal one, enlarged. (Baillon.) 



view it as an elongated leaf in which the framework was at 

 first divided palmately into three branches, the middle one 

 of which again divided similarly, and this method of branch- 

 ing continued during the elongation of the blade. However 

 we may view the nervation, such a leaf in which a single 

 midrib, or direct continuation of the petiole, gives off several 

 or many lateral branches, is distinguished as pinnately nerved. 

 The leaves of the pasque-flower are described as pinnately 

 compound or pinnate.- The leaflets of the Christmas rose are 

 pinnately nerved, the leaf as a whole being palmate or pedate. 



' Cos'-tate < L. cosia, a rib. 



- Pin'-nate < L. pinna, a feather, because the veins arise from the 

 midrib as do the barbs of a feather from its shaft. 



