THE ANATOMY AND AFFINITY OF PLATYZOMA MICROPHYLLUM. 651 



small spores. In the first of these there were 14 spores of the largest type and 

 two of the intermediate size ; in the second instance there were 14 large spores and 

 one small spore. It is impossible to decide at this point whether there is here a 

 true heterospory, or the variation in spore size is merely the result of peculiar 

 local nutritive conditions. I have not yet examined the contents of these 

 remarkable spores, and accordingly can give no indication from this standpoint of 

 the significance of the variation in spore size and output per sporangium. It is 

 hoped to throw more light on the nature of these spores when the development of 

 the sporangium has been studied and the spores can be germinated. But while 

 in general form of sporangium, and obliquity and irregularity of the annulus, 

 Platyzoma somewhat resembles some species of Gleichenia, the differences of 

 sporangial and spore size and the small spore output are not characteristic of any 

 known Gleichenia. 



The chief facts obtained from the specimen of Platyzoma have now been 

 considered. The habit of the plant, upon which the systematists chiefly relied, 

 has sunk in importance before the remarkable characters of the stele, the leaf- 

 traces, the leaves, and the sporangia. This plant has proved anomalous at almost 

 all points, and in fact it would be difficult to indicate any known Fern with which 

 Platyzoma can be reasonably compared. One is forced to the conclusion that it 

 is not a Gleichenia. The development of the sporangia and the true nature of 

 the spores may throw a fuller light upon its true affinity ; and until information 

 on these points is forthcoming, it would be foolish to separate Platyzoma from a 

 relationship which may prove to be its nearest affinity. But although one cannot 

 speak with any degree of confidence regarding the actual place of Platyzoma in 

 the phyletic system, the study of its anatomy has laid bare facts regarding the 

 stele, reduction processes in the leaf, and sporangial characters which may be of 

 value in later discussions. The material available for the investigation was an 

 herbarium specimen, and accordingly it was impossible to do more than collect 

 the most important facts of mature anatomy. The present memoir is to be regarded 

 as an instalment of the facts relating to this remarkable Fern, and the statement 

 is not to be considered a final one. This being so, it has been thought well not 

 to enter upon detailed comparisons, though the remarkable facts relating to 

 Platyzoma provoke them. It has likewise been deemed well to abstain from any 

 very definite statement as to the systematic position of Platyzoma until the 

 sporaugial conditions have been more fully examined. These matters can be better 

 dealt with when properly preserved materials are available. 



I am indebted to the Director of Sydney Botanic Garden for the specimen upon 

 which these observations have been made ; to Professor Bower for much valuable 

 guidance and criticism ; to Mr Boodle for information regarding the Kew specimens 

 of Platyzoma, and to the Carnegie Trust for their assistance in the production of 

 the illustrations. 



