Hart's-Tongue 45 



IN the development of the leaf of Phyllitis scolopendrium the 

 blade assumes successively the following forms: spatulate; spatu- 

 late-oval or suborbicular; suborbicular or roundish-ovate or 

 ovate-oblong, becoming cordate; ligulate-cordate ; and oblong- 

 lanceolate or lanceolate or linear-lanceolate with cordate or auric- 

 ulate base. 



The spatulate leaf contains either a simple vein or an incipi- 

 ent midvein which does not extend beyond two basal primary 

 branches. The midvein is evident in succeeding leaves. It 

 gradually lengthens and sends out successive primary branches, 

 and is finally contained in a midrib. 



The basal primary branches of the midvein may be once 

 forked or even occasionally simple at first. They vary, but are 

 mostly more complex than the primary branches above them. 

 As development of the blade progresses they branch more and 

 more, and in the mature leaves are markedly complex. 



The primary branches above the basal mostly vary at first 

 from simple to once forked, but gradually become more com- 

 plex. In the mature leaves they vary from once to three times 

 forked, excepting the extreme uppermost, which, appearing later 

 than those below, sometimes do not develop beyond the simple 

 stage. 



The veinlets are mostly clubbed at apex. They end near the 

 leaf's margin: the veinless border is often pronounced. 



Occasional areolae occur in the mature leaves. I have seen 

 only one areole, near the midvein of a very small leaf, in the 

 young leaves. 



At first the leaf-blade is decurrent on the petiole so much 

 so in the narrower of the spatulate leaves that the petiole resem- 

 bles a winged midvein. 



