218 Mr. D. Don's Descriptions of new Genera and Species 



cumference are clearly nothing more than the scales composing 

 the inner series of the involucrura. The plumose pappus com- 

 pared with that of the inner floret of the partial capitula of 

 Polyachyrus, a genus hereafter to be described, the form and 

 structure of their corolla, the outer lamina of which is tra- 

 versed in both by four distant slender nerves, and the habit of 

 the plants themselves, show that there is a considerable degree 

 of affinity between these two genera. 



Ptilurus. 



FloscuU fequales. Pappi radiis plumosis, duplici serie dispositis. 

 Involucrwn subaequale. 



Involucrum duplici ordine poly-(18 — 20)phyllum, subaequale: 

 foliolis ovato-lanceolatis, trinerviis, apice membranaceo 

 acuminate radiatis. Receptacidum nudum. FloscuU omnes 

 hermaphroditi, tubulosi, bilabiati, eequales ; labio exteriore 

 ligulato, 4-nervio, obtusfe tridenticulato ; interiore bipartite, 

 demilm revoluto : segmentis linearibus, obtusis, binerviis. 

 Anthera coalitae, basi longfe bisetosse : setis simplicibus : 

 appendiculA lineari-lanceolata, acutd. Stigma bipartitum : 

 laciniis semicylindricis, recurvis, apice dilatato-truncatis, 

 pruinosis. Achenia elliptico-oblonga, compressa, dens^ pa- 

 pilloso-glandulosa, apice angustata, disco parvo. Pappi 

 radiis crassiusculis, eleganter plumosis, mollissimis, duplici 

 ordine digestis, basi dilatata imbricatis ! deciduis. 



Herba perennis, humilis, ccespitosa, facie Dauci v. Athamantce, 

 setulis erectis, gland ulifer is, copiosissime instructa. Radix 

 fusiformis, ramosa. Caulis erectus, teres, subramosus, tri- 

 uncialis, vix calami scriptorii crassitie. Folia supradecom- 

 posita, dens^ glandulosa, pollicaria v. sesquipollicaria : seg- 

 mentis linearibus, obtusis, sesquilineam longis. Petioli foliis 

 longiores, maxime dilatato-membranacei ; inferiorum foliorum 



latiores 



