PERN ALLIES OP NEW ZEALAND. 17 



different tribes. These capsules are usually oblong or orbicular, 

 and furnished with a short stalk ; while over them commonly 

 passes a more or less complete ring or annulus (PL I. fig. ia), which 

 by its elasticity serves to rupture the capsule and liberate its 

 contents. There is only one kind of spore. New Zealand contains 

 29 genera, including 124 species — a large number compared with 

 Britain, which only has (according to Sir J. Hooker) 1 3 genera and 

 37 species. 



Ferns are divided into eight tribes, of which seven are represented 

 in New Zealand. Their characters will be found in the next chapter. 



Order II. — Ophioglossacese is a small group, often included 

 among true ferns, but differing from them in some important respects. 

 The short subterranean rhizome sends up only one leaf, or at the 

 most two or three, and these are not rolled up in the circinate manner 

 characteristic of ferns. They take, also, a very long time to develop, 

 those of Botrychium being four years of coming to maturity, of 

 which three are spent underground. The spore-capsules are not 

 collected into sori, but are arranged either in a spike or raceme-like 

 cluster on a special fertUe frond. They have no ring, and contain 

 smooth triangular spores. Lastly, their prothallus, produced from 

 one of these spores, is not a flat layer of cells, but a subterranean 

 mass of cellular tissue, destitute of green colouring matter. Only 

 three species belonging to this order occur in New Zealand. 



Order III. — Marsileacese. All the plants of this order are aquatic 

 or marsh-dwellers, and their fronds expand in a circinate manner 

 like those of ferns. At the base of the fronds and near their creeping 

 rhizome the organs of fructification are found. These organs are 

 really formed from modified infolded leaves, and in our plant 

 (Pilwlaria) are small oblong capsule-like bodies (the sporocarps), 

 borne on short stalks and opening by 2 (or 4) valves. If cut 

 transversely, these capsules are found to be 4-celled, or divided into 

 4 cavities, each cavity containing a number of oval or egg-shaped 

 bodies. Those near the bottom of each cavity are termed macro- 

 sporangia, because each contains only one large spore, the Tnacrospore. 

 Those in the upper half of the capsule are microsporangia, and 

 contain each from 20 to 30 most minute granules — the microspores. 

 The latter are the male reproductive organs, while from the 

 macrospore the prothaUus is developed. 



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