12 Transactions. 



mens I saw were in cultivation on the island ; and in one case apparently 

 on the same plant I saw normal fronds of A. nidus growing, together with 

 the abnormal fronds of A. Robinsonii. However, it is not quite extinct. 

 The late Mr. Robinson sent away all the plants he could find of it. Mrs. 

 W. Laing has, however, recently (1914) found young specimens on different 

 parts of the island. It is a much less luxuriant plant than A. nidus, and its 

 fronds do not appear to reach 2 ft. in height. The fronds are always petiolate 

 and usually crested and incised but occasionally entire. As in A. nidus, 

 the sori are usually confined to the upper part of the frond, and, though 

 sometimes not reaching to the midrib, they do not differ from A. nidus 

 in this respect. Thus the reproductive distinctions relied upon by Baron 

 von Miillerf scarcely seem to exist. The distinctions in form, size, incision, 

 and lobing of the frond are undoubtedly sufficient to form a good species, 

 did one not know that such variations occur not unfrequently as recognized 

 sports in similar ferns. Thus the forms of A. nidus and A. Robinsonii are 

 exactly paralleled by the mutations of the hart's tongue fern, Scolopendrium 

 tmlgare.% 



The less luxuriant habit and the constant petiolation are perhaps cha- 

 racters of more importance than the varying incision and lobing of the leaves, 

 and may justify the retention of this as a distinct species. 



16. Asplenium difforme R. Br., E. 28. (= A. obtusatum Forst. var. 

 difforme, M. 32.) 



Australia. 



I cannot agree that this is only a form of A. obtusatum, in spite of the 

 weight of opinion against me — e.g., Hooker and Baker, Maiden, Christiansen. 

 The plant grows abundantly on the coastal rocks both of Norfolk Island 

 and Phillip Inland, and shows great variety in the division of its fronds ; 

 but at no time is it similar to the common form of A. obtusatum as met with 

 in New Zealand. Indeed, it approaches closely at times to A lucidum var. 

 Lyallii. Further, I cannot bear out the statement of Backhouse (3), to 

 whom we are indebted for an excellent general description of the character 

 <if the flora before it was overrun by weeds. He, speaking of this fern, 

 states that " at a short distance from the shore its leaves become more divided, 

 and in the woods in the interior of the island they are separated into such 

 narrow segments that the lines of fructification are thrown upon the margin." 

 The plant only grows on rocky shores, and does not occur inland, and the 

 ironds on one rootstock are often polymorphous. Three types of pinnae 

 may perhaps be distinguished, but intermediates are abundant. 



(a.) The pinnae are 5-8 cm. long, 12-15 mm. broad, lanceolate to oblong 

 in outline, crenate-dentate at the top, pinnatifid towards the middle and 

 pinnate at the base ; thus much resembling A. lucidum var. Lyallii. 



(b.) The pinnae are 1-2 cm. long, 8-10 mm. broad, ovate to ovate- 

 elliptical with well-rounded apex, dentate in the upper half, and lobed 

 towards the base. They are altogether smaller than in form (a). 



(c.) The pinnae are much more incised, and the pinnules approach 

 those of typical A.flaccidum, being linear and acute or acuminate. 



I admit, of course, that intermediates are so common in this genus that 

 it is difficult to separate the various species, but the character here insisted 



t " Journal of Botany," xxii, p. 289. 



t Vide J. A. Thomson: Heredity; fig. 22, p. 99 (Mutations of Hart's Tongue 

 Fern). 



