142 Transactimis. 



Mention lias already been made of two plants {Metrosideros villosa and 

 Nothopanax arboremn) which frequently pass through the first stages of their 

 development on tree-fern stems, but subsequently become connected with 

 the ground by their roots. 



(4.) Ferns : Ferns may conveniently be divided into three ecological 

 groups — tree-ferns, filmy ferns, and other kinds. 



The first group is represented on Sunday Island by two endemic species, 

 which, however, differ in many important points. 



Cyathea kermadecensis is characteristic of the wet forest, and in places 

 is the dominant plant. What may be termed a Cyathea forest exists in 

 places, where magnificent tree-ferns, 20 m. tall, form a distinct plant 

 association, forest-trees taking but a subordinate part. The fronds are 

 rather flaccid in texture, and in dry weather curl up their pinna-segments. 

 As they wither they fall, leaving the top of the trunk bare, and this habit 

 gives the fern its graceful appearance. Adventitious roots are developed 

 at the base of the trunk until it assumes large dimensions. Growing on 

 hillsides the plants are usually leaning, and the adventitious roots are given 

 out most abundantly on the under-side, where most of the rain-water 

 running down the stem naturally flows before reaching the ground. Here 

 the base of the trunk forms an acute angle, and a cross-section would be 

 somewhat kite-shaped, about 2 m. one way and 1 m. the other. 



Cyathea Milnei, the more common tree-fern in dry forest, has hard 

 coriaceous fronds, which clothe the top of the trunk as they wither. 

 Adventitious roots form a conical base sometimes nearly 1 m. in diameter. 



The filmy ferns, of which there are four species on Sunday Island, have 

 delicate fronds formed of but a single layer of cells. In dry Aveather the 

 fronds curl up and the tips wither to a certain extent, and, if the drought 

 be lasting, do not recover; hence it is a common thing to see these ferns 

 with the edges of their fronds dead. 



Hymeno'phyUum demissum is abundant everywhere in wet forest, on 

 branches of trees, tree-fern stems, and on the ground. Large fronds 

 measure, including the stipes, 36 cm. in length. In dry forest a few small 

 sickly-looking plants were noticed on a log in Denham Bay. H. flabeUatum 

 was found in one place only — the matted roots and close fronds covering 

 the under-side of a leaning trunk of Metrosideros villosa on the summit of 

 Moumoukai. The fronds M-ere small, 6-7 cm. long, with close overlapping 

 segments, dead at the tips, and filiform stipes, 1-14 cm. in length. 



Trichomanes humile, with fronds 7-11 cm. long, was extremely rare, 

 being found only on wet banks and fallen trunks of tree-ferns in deep shady 

 ravines. T. venosum is an epij)hyte of the wet forest found only on the 

 rmder-side of leaning trunks of Cyathea kermadecensis. In its ordinary 

 state the frond is broadly ovate, 7-8 cm. long, 3-5 cm. broad, with a short 

 filiform stipe 2-3 cm. long ; but when growing far in under a trunk it is 

 linear, 11-14 cm. long, 1-5-2 cm. broad, with a stipe 2-5-5 cm. long. One 

 frond, including stipe, measured 17-5 cm. in length, 2 cm. in breadth. 



Of other kinds of ferns entering largely into the forest formation Pteris 

 comans, Polystichum aristatuni, and Nephrolepis exaltata are the chief in 

 dry forest. All have coriaceous fronds. In wet forest Dryoperis glabella 

 and Blechnum norjolkianum are abundant. The texture of their fronds is 

 firm but scarcely coriaceous, and in their you]ig states very delicate. 

 B. norjolkianum often has a small erect rhizome 10 cm. high, bearing the 

 fronds in a tuft near the top. 



