PHYTOLOGY. 



ON OEETAIN LICHENS BELONG-ING TO THE GENUS 



PAEMELIA. 



Pa' JAMES STIRTON, M.D., F.L.S. 



CONSIDERABLE attention has lately been bestowed on 

 the spermogonia and spermatia of lichens, mainly as a 

 means of discriminating genera and species. The relationship 

 of these organs to the apothecia is far from being satisfactorily 

 determined, inasmuch as direct experiments bearing on the 

 question are awanting ; and it is only by way of analogy that a 

 presumption is afforded that they play the same role as the 

 antheridia of mosses to the archegonia. The constancy in size 

 and configuration of the spermatia in the same lichen is re- 

 markable considering their minuteness, and warrants their im- 

 portance as a means of diagnosis in critical cases. 



Since the publication by Dr Nylander in t86o of his *Syn. 

 Meth. Lichenum,' considerable diversity in the form and size of. 

 the spermatia in the Pai'melicE has been discovered. Indeed, with 

 the exception of two Australian species, all the others were then 

 reckoned to have bifusiform spermatia. This is now known to 

 be far from true. In one instance — viz., P. pei'foi'ata., I am still 

 in doubt whether the European and North American forms 

 (which certainly differ, in outward form at least, from specimens 

 received from the southern hemisphere) have bifusiform spermatia 

 or not, inasmuch as the two specimens at hand are destitute of 

 spermogonia. It is rather curious also, that amongst all the 

 magnificent fruiting specimens received from South Africa, not 

 one spermogonium containing spermatia has been detected. 

 However, from Australia and New Zealand, whose lichen floras 

 l^ossess several remarkable points of resemblance to that of 

 South Africa, I possess specimens bearing spermogonia contain- 

 ing spermatia. In these, the spermatia are exactly cylindrical, 

 and longer than usual. Until this question is definitely settled, 

 any conclusions as to the diversity or identit}- of the s])ccimens 



