Carse. — Ferns and Fern Allies of Mangonui County. 89- 



Abnormal Forms among Ferns. 



Probably among no other class of plants are abnormal habits of growth 

 so common and so varied as among ferns. Many of these forms are so 

 persistent as to have become recognized as distinct varieties, or even 

 distinct species. In many cases a clear series of gradual changes can be 

 traced from one extreme form to another ; in others the strange forms 

 produced are clearly " sports," eccentricities caused by environment, an 

 unusual luxuriance manifested in extraordinary development of some 

 feature of the plant or a depauperation due to the xerophytic conditions 

 under which the plant has grown. In some cases these strange forms 

 become permanent, thus establishing a variety ; in others the plants 

 being removed to more favourable habitats become normal. Some of 

 these forms may arise from cross-fertilization in the prothallial stage. 



That such intermediate forms do exist is clear to all who have studied 

 the various states of Doodia media and D. caudata, of Asplenium balbi/erum 

 and A. Hooherianum, or of Todea hymenophyUoides and T. superba, forms 

 of which it is almost impossible to describe as belonging to either of the 

 plants in the pair under consideration. 



For some years I have noted and collected abnormal growths among 

 ferns, and I propose to set down some of my observations, not so much 

 to increase the knowledge on this point, but rather to elicit further infor- 

 mation on a point of no little interest. 



Hymenophyllum. 



Irregularities in this family are apparently rare; bifurcation of the frond 

 is all I have noticed, and that only in 11. demissum, the commonest of 

 them all. 



Cyathea. 



C. medullaris and C. dealbata, especially in the juvenile form, frequently 

 have the ends of one or more of the primary ferns bifurcated. 



Hemitelia. 



I have noticed a similar bifurcation in young fronds of this species, 

 but all who are interested in this subject should refer to vol. 19 of the 

 ' ; Transactions of the New Zealand Institute," where Mr. Buchanan figures 

 and describes a remarkable plant of this species having 16 branches. 



Lindsay a. 



Of L. linearis I have a very curious form, collected by the late Mr. 

 Andrew Thompson, of Aponga, in the Whangarei district. The fertile 

 frond in the lower half is distinctly bipinnate, having adventitious rhachides 

 bearing stipitate pinnae : higher up the pinnae are divided into 2-3 stipitate 

 lobes. 



L. cuneata has the upper part of the frond divided into two branches 

 occasionally. The occurrence of bipinnate and simply pinnate fronds on 

 the same plant has already been referred to. 



Adiantum. 



Among the maidenhairs I have seen but few abnormal forms. 

 In A. diaphanum which is simply pinnate, or with one or two branches 

 at the base of the main pinna, occasionally one of these branches is again 



