54 A CONTRIBUTION TO, ETC. 



tenuifolia is a very common species in Australia, varying consider- 

 ably in size and appearance according to the degree of moisture 

 to which it is subjected, being sometimes only two or three inches 

 high, and sometimes more than a foot. C. Sieberi seems to be a 

 mere variety of a more rigid habit, whilst C. caudata, which is not 

 well-known, has an affinity to it, but has very elongated termi- 

 nated pinnules, both at the main apex of the frond and on the 

 branches. Whether C. Pressiana from Swan River is a distinct 

 species, or whether all our known species of Cheilanthes are to 

 be regarded as mere varieties of one common type, remains to 

 be shown. 



Brown's Pteris falcata and Adiahtum paradoxum are now re- 

 ferred to the genus Pellcea, so called from pellos, " of a dark 

 colour," because the genus comprises plants with brown or black 

 stipes. P. paradoxa has been rather a perplexing one to col- 

 lectors on account of the great variation to which it is subject, 

 and it seems highly probable that hereafter it will be regarded as 

 a mere variety of P. falcata, with which also P. rotundifolia of 

 New Zealand will be associated. Sir W. Hooker, judging from 

 dried specimens placed in his hands, could see no difference be- 

 tween P. paradoxa and P. falcata, " except the usually taller, 

 but narrower and more numerously pinnated fronds, with nar- 

 rower pinnae, and stipes and rachis squamuloso-hirsute." The 

 identity of the so-called species, however, is more evident from 

 seeing the variations in a living state, and noticing how gradually 

 they pass into each other. If, indeed, we were to take the ex- 

 treme varieties of these ferns, Ave might imagine them to be dis- 

 tinct species, as many botanists have done who had no oppor- 

 tunity of examining living specimens ; but when we can find so 

 many connecting links between them, we must be led to a differ- 

 ent conclusion unless, indeed, we regard every deviation from 

 the original type as an indication of a new species, and then we 

 may make as many species as there are varying forms. 



The next genus to be considered is Pteris, which differs from 

 the preceding in having " sori arising from a longitudinal con- 

 tinuous receptacle in the axis of the involucre," whereas in Pellcea 

 the sori are in reality separate in the first instance, although 

 eventually they become confluent. There are some species of a 

 doubtful character, vacillating as it were between the two genera, 



