n8 ANNALS OF SCOTTISH NATURAL HISTORY 



extent by one of the most eminent authorities on the genus 

 of the present day, it will be well, in the first place, to note 

 the dissimilarities by which the two species may be most 

 readily separated, especially in the dried state, when the stem 

 characters are not readily available. 



In P.prcelongus the leaves are more distinctly hooded at the 

 tip, I 3-2 1 -ribbed, translucent, with numerous distinctly visible 

 transverse reticulations ; the peduncles are stout, slightly 

 swollen upwards, and always considerably exceeding the sub- 

 tending foliage. In P. undulatus, the leaves are but slightly 

 hooded, or even flattened at the tip, 5-7-ribbed, with few 

 widely separated transverse reticulations which are often 

 hidden in the opaque substance of the leaf; and the peduncles 

 are slender, equal, and much shorter than the subtending 

 foliage. 



Rcemer and Schultes placed undulatus under P. crispus 

 as a variety or subspecies ; guided, no doubt, by the com- 

 pressed stem and by the early foliage, which often closely re- 

 sembles that of crispus. From this, however, the entire margins 

 of the leaves, like those of perfoliatus, afford a clear distinction 

 at all times. Although, as in the latter species, the margin 

 is furnished towards the tip with minute spines, it is never 

 serrulate like that of crispus. 



Mr. Lees provisionally placed his " var. Jacksoni " under 

 P. perfoliatus, apparently not having attached much import- 

 ance to the compressed stem ; and possibly, also, from not 

 having characteristic examples of the early states of the plants 

 submitted to him. However this may be, P. undidatus v. 

 Jacksoni has found its place into our lists as " P. perfoliatus 

 v. Jacksoni " and it is necessary to point out the best way of 

 separating all perfoliatus-Yike states of P. undulatus from the 

 older species of Linnaeus. P. perfoliatus has amplexicaul, 

 cordate, many-ribbed leaves, and the stipules are rarely to be 

 met with except with the youngest shoots and leaves, and the 

 lowest one is very rarely expanded into an ear-like imperfect 

 leaf ; whilst in P. undidatus the leaves are semi-amplexicaul, 

 not cordate at the base, and few-ribbed, and the stipules are 

 more persistent, with the lowest, on both stem and branches, 

 frequently furnished with a small distinct leaf on the back, 

 resembling the ordinary leaves. Practically this distinction 



