[62 



SCHIZAEACEAE 



[CH. 



assembled according to that character by J. Smith under the name of 

 Hydroglossum, the veins show occasional fusions. Those species have, how- 

 ever, been separated again by Prantl on the ground of geographical 

 distribution. It seems probable that the adoption of vein-fusions might 

 have been more than once effected independently in different geographical 

 regions, as an amendment in the structure of a broadening leaf In any 

 case the existence of a reticulum is regarded as a derivative state. 



A similar view may be entertained for Anemia. The simplest leaf is that 

 of the small Brazilian species distinguished generically as TrocJioptcris by 

 Gardner, but merged by Prantl as 

 a sub-genus of Anemia. The open 

 venation is identical with that of 

 a young leaf of Osmunda, or of 

 Anemia{com\idire. Fig. 4i6,/and^'-), 

 while the two lowest pinnae may 

 be fertile as in the latter (Fig. 446). 

 Larger species of Anemia exhibit 

 simply a further elaboration of that 

 plan (Fig. 440; also Fig. 77, Vol. i). 

 The open venation is retained, ex- 

 cept in the broad-leaved A. PJiylli- 

 tidis Sw., and some less-known 

 species grouped by J. Smith as 

 \Anemidictyon. Here occasional 

 anastomoses give a coarse reticulum, 

 as in Lygodiiim ; probably a late and 

 derivative consequence of widening pig. 446. Fertile leaf of Anemia [Trochopteris) 



of the leaf-area. Clearly the ori- 

 ginal and typical vein-branching of 

 Anemia was dichotomous, as it is 

 also for the rest of the family. The 

 different genera show various steps 

 from equal dichotomy to pronounced dichopodial development, and from 

 single-veined segments to advanced webbing. The former is seen very 

 perfectly in A. millefolia, where the sterile blade is highly cut so that each 

 lobe contains only a single vein, after the manner of Sphenopteris. Webbing 

 appears in various degrees in Schisaea, while occasionally it has led in 

 Lygodium and Anemia to the further step of vein-fusion. It is thus possible 

 to trace in the leaf-architecture indications which lead the eye to recognise, 

 within the family, signs both of the simple beginnings as simple-veined 

 bifurcation, and of the climax as a reticulate expanded blade. 



The origin of the pinna-trace is uniformly marginal in the Schizaeaceae, 



elegans, drawn from a specimen in the Glasgow 

 University herbarium, and showing sympodial 

 dichotomous branching of its veins: i-iv = succes- 

 sive pinnae : the two basal pinnae are fertile, but 

 sporangia are sometimes found on the upper seg- 

 ments or at the distal end, as in other species of 

 Anemia. (SeealsovonGoebel,/"/i3ra, 1915.) ( x 4.) 



