546 INTRODUCTION TO CRYPTOGAMIC BOTANY. 



slum ; but this is sometimes entirely wanting, and the sporangia 

 are produced upon a distinct hairy receptacle. Oyathea has 

 free veins or veinlets, numerous sporangia, on a raised or club- 

 shaped receptacle, surrounded by a spherical indusium, bursting 

 above or below, and forming a cup round the sorus. In Schi- 

 zocmna the sori are seated on the middle of the veins or vein- 

 lets, and the indusium has six lobes, like little petals, surround- 

 ing a globose receptacle. In Hemitelia, united with Cnemi- 

 daria by Smith, the lower pair of veinlets anastomose, and 

 the indusium is a mere scale, which leads to the Polypodiaceous 

 genera, in which the place of the indusium is sometimes sup- 

 plied by hairs or scales. Alsophila, Oymnosphaira, and Tri- 

 chopteris, differ more in habit than in technical characters. 

 In Alsopliila the receptacle is mostly hairy, the leaves are 

 decompound, and the stipe often prickly. In Gytnnosphcera 

 the fronds are bipinnate and sometimes prickly, and the sori 

 quite naked, with the sporangia on a subcylindrical receptacle. 

 In Trichopteris the receptacle is oblong, hairy, and the sori 

 laterally confluent, so as to form transverse linear heaps of 

 sporangia. In this, also, the leaves are bipinnate, and the 

 habit different from Alsophila. In Metaxya the fronds are 

 simply pinnate. Each fertile vein bears several sori, a cir- 

 cumstance quite peculiar to the genus. This differs, moreover, 

 in its spores not being triangular. There is a peculiarity about 

 Alsophila capensis which deserves notice. On the lower part 

 of the stipes, and especially that part which joins the caudex, 

 abortive pinnae are formed, reduced almost to the rachis, and 

 resembling so closely some Hymenophyllum or Trichomanes, 

 that Kaulfuss has described them with a note of doubt under 

 the name of Trichomanes cormopUyllum* In the plant as 

 cultivated at Kew their identity with the pinua3 is evident, as 

 pinniE of the normal form are often intermixed with others 

 consisting of a rigid costa and narrow hyaline border. The 

 delicate and beautiful fronds of Gyathea Smithii are with much 

 good taste used by the New Zealanders to adorn their meeting- 

 houses. 



* See Hook. Sp. Fil., vol. i., p. 37. It is to be observed that the 

 structure of the altered frond is quite unlike that of Trichomanes. 



