6i6 FILICALES 



of the sori and the habit, as well as by certain anatomical features. The 

 genus appears to hold an intermediate position between the Dennstaedtiinae 

 and some Ferns referred to Polypodium : the relationship to the latter 

 has already been the subject of remark ; for instance, in the Synopsis 

 Filicum, p. 130, Dr. Griesebach is quoted as writing of H. Purdieana, Hk. : 

 " Not to be distinguished from P. rugtdosum but by the specially transformed 

 involucral appendages, and probably passing into that widely-ranging species." 

 Again, 1 under Polypodium (Pheg.) punctatum, Thunb. (which Hooker 

 regarded as including P. rugulostim, Labill), he remarks : " Very closely 

 related to Euhypolepis" All this seems to indicate a probable sequence 

 which would consist of (a) some Dennstaedtiinous Ferns with basipetal 

 sori, (b] some type with mixed sorus, and receptacle within the margin 

 which is curved over as an indusium, as in Hypolepis : (c) such -a type as 



Polypodium punctatum, Thunb., with 

 its definitely superficial, unprotected 

 sorus, having sporangia with ages inter- 

 mixed, and no regularity of orientation. 

 It may next be enquired how far 

 the anatomical data will support the 

 results of examination of the sori in 

 this series. It cannot be assumed that 

 characters so distinct as those of the 

 sorus and of the vascular system 

 FIG. 342. must necessarily run parallel ; but if 



r Pteris elata, \. Karsteniana. Diagram showing they do, it is a Strong Support of the 



the arrangement of the vascular tissue at the _ . . 



insertion of a leaf. A piece is supposed to be cut Correctness OI recognition OI a phyletlC 



out of the side of the solenostele, so as to show the ,- .-^ -vruur iu 



internal vascular system. Note that a small strand, Une. UWVline- VaUghan has lOUnd that 



lying within the second vascular ring, is also present. r L u j. *i_ 



(After Gwynne-Vaughan.) m CVCry SpCClCS of the SUb-tribC 



Dennstaedtiinae in which the anatomy 



is known the same type of primitive vascular system, the solenostelic, is 

 seen : this indicates the primitive nature of Prantl's sub-tribe as a whole. 

 The statement applies for all species of Dennstaedtia examined, but in 

 D. rubiginosa the solenostele is not quite typical, additional vascular 

 strands being also present : this is, however, the very species in which 

 an approach to a mixed sorus is found : thus, the two characters indicate 

 that plant as an advance upon the rest. The approach is towards a 

 condition seen in species of Pteris, where with a mixed sorus there is a 

 still more elaborate accessory vascular system within the original soleno- 

 stele (Fig. 342). 



Turning to the Hypolepis-Polypodium line above noted, the anatomy 

 again supports the relationship. Hypolepis is solenostelic : so is P. punctatum : 

 in fact this species stands structurally isolated among the Polypodieae, and 

 is evidently related closely to Hypolepis, which in turn is related to the 

 other Dennstaedtiinae. 2 



1 Syn. Filic., p. 312. - Gwynne-Vaughan. I.e., p. 735. 



