502 



FILICES. 



DlCKSONIA. 



***** Dicksoni^;, J. Sm. Sori marginal, globose or oblong, furnished with a special involucre which 

 is attached to the inner side, and is combined more or less with the altered margin of the frond, 

 thus becoming urceolate or 2-lipped. 



16. DlCKSONIA. VHerit.; Hook. gen. Fil.t. 61. dicksonia. 



[In honor of James Dickson, an English cryptogamic botanist.] 

 Sitolobium, Dcsv.; Patania, Presl. 



Sori small and roundish, situated at the margin of the frond, and arising from the apex of a 

 vein. Involucre coriaceous or membranaceous, formed in part of the lobule of the frond 

 and of the proper involucre more or less united, 2-valved or entire, sometimes cup-shaped. 

 Receptacle elevated, globose. Frond usually much divided ; the veins pinnated, simple 

 or forked : veinlets free. 



1. Dicksonia pilosiuscula, Willd. Hairy Dicksonia. 



Frond bipinnate ; pinnag lanceolate, rather obtuse, deeply pinnatifid ; segments incised- 

 toothed ; sori minute, one in the sinus of each segment ; involucre cup-shaped ; rachis and 

 stipe glandularly pubescent. — Willd. sp. 5. p. 484 ; Pursh, fl. 2. p. 671 ; Bigel. fl. Bost. 

 p. 395 ; Beck, hot. p. 456 ; Darlingt. fl. Cest. p. 584; Hook. fl. Bor.-Am. 2. p. 264. D. 

 punctilobula, Hook. sp. Fil. p. 79. D. pubescens, " Schk. Fil. t. 13." Nephrodium puncti- 

 lobulum, Michx.fl. 2. p. 268. Aspidium punctilobum, Willd. I. c. ; Pursh, I. c. A. punc- 

 tilobulum, Torr. compend. p. 382. Sitolobium pilosiusculum, Desv. ; J. Smith, I. c. 



Frond 15 - 20 inches high, ovate-lanceolate, acuminate, somewhat hairy, of a pale green 

 color, but yellowish when dry ; the lower pinna? 3-4 inches long and an inch in width : seg- 

 ments 6-8 lines long. Stipe and rachis sparingly clothed with short somewhat glandular 

 hairs. Sori minute, one (rarely two) on the upper margin of each lobe of the segments, at 

 the lowest tooth. 



Moist shady places : common. Fr. July. This is the only species of Dicksonia inha- 

 biting temperate climates. The outer half of the cup-shaped involucre is formed of the 

 inflexed margin of the frond. It is of a firmer texture than the inner portion, which, indeed, 

 is the true involucre, and with which the marginal portion is confluent. 



Suborder II. OSMUNDEiE. Martius. The Flowering-fern Tribe. 



Capsules destitute of a ring, reticulated, pellucid, striated with rays at the apex, 

 bursting lengthwise on one side. — Rhizorna creeping or short. Fronds mostly 

 pinnated. 



