272 



DICKSONIACEAE 



[CH. 



539, D). Similar conditions are occasionally seen also in Microlepia hirta, 

 though in that genus the basipetal succession appears to be the rule (Fig. 

 540). The importance of these deviations will become apparent as our 

 comparisons proceed. Meanwhile they should be carefully noted, with the 

 general remark that they point in the direction of that large body of Ferns, 

 of which Davallia is a central type, in which the marginal sorus is of the 

 "mixed" type. 



Saccolovia which was associated by Prantl with the other Dennstaedtiinae, 

 stands out from the family as advanced in its vascular system, and in its 

 flattened dermal scales. It is also rather distinct in habit, the stock being 



Fig. 540. A, Microlepia spelimcae (L.) Moore. Sorus showing unequal lips of the indusiuiii, 

 and basipetal succession of the sporangia, (x 100.) B,C, Mitro/epia hiria\\.a.\.\\i. Similar 

 sections to A but showing departures from the strict basipetal succession. { x 100.) 



upright and radial, while the leaves are simply pinnate. The pinnae are as 

 much as a foot long, traversed by parallel, occasionally forked veins, upon 

 the ends of which in fertile pinnae the sori are borne in an apparently intra- 

 marginal row. The relations of the sori have been elucidated by von Goebel 

 {Orgajiographie, II Aufl., p. 1 143). What appears as a continuous leaf-margin 

 is really composed of the upper indusial flaps of a row of sori fused laterally. 

 The upper flaps are larger than the lower, and the latter appear intra- 

 marginal, covering the still distinct receptacles. Seam-like swellings of the 

 upper flap indicate the limits of the partially fused sori (Fig. 541,^). Com- 

 paring this structure with that seen in Microlepia pi atyphylla, and these again 

 with Nephrolepis or with Lindsaya, we see in these Dennstaedtiinae ferns 



