Auslralian and Tasnumian Xlmlelllferons Tlants. 235 



Plati/carpidimnJ from Astrotricha in deciduous petals, from 

 Trachymene in flat and smooth carpels, from Platysace, as 

 far as the immature state of the fruit permits me to judge, 

 by the want of vittas, and from Bidiscus and most of the 

 allied genera by a tall shrubby habit, so unusual in this 

 order, and, finally, in a paniculate disposition of its umbels, 

 of which the greater number, notwithstanding their being 

 hermaphroditical, remain perfectly sterile. 



Besides the description of the new Eryncjia, I beg to sub- 

 mit an enumeration of all the species of Bidiscus with which 

 we are at present acquainted. Those of the sub-genus 

 Hemicarims have been considered formerly by the author of 

 this treatise as constituents of a new genus, and are described 

 as such in Hooker's Kew Garden Miscellany of this year. 

 Observing, however, on a re-examination of all the material 

 now at my command, that one of the mericarps, sometimes 

 in several species of i)i^Mc«^6f, and often in Bidiscus pilosus, 

 remains undeveloped, — I prefer now to reduce Hemlcarpus 

 to this genus. 



Thus another is added to already numerous instances to 

 prove how much often the best characteristics, which are 

 adopted in botanical science for the division of species into 

 groups, fluctuate. Nature, which created but species, steps 

 with an easy pace over the arbitrary generic limits within 

 which we narrow and unite for the facilitation of study every 

 complixity of closely allied forms. We will ever, therefore, 

 remain at variance in opinion what limits to assign to 

 genera, but we ought by useful research to arrive at last at 

 one and the same result as to the true precincts of species. 



Eryngium plantagineum. 

 Erect, glabrous ; stems furrowed, the lower part leafless, the 

 upper part paniculate ; radical leaves long or lanceolate- 

 linear, entire or with remote thorny teeth or with narrow 



2 H 



