TRANSACTIONS 



OF THE 



NEW ZEALAND INSTITUTE 



1907. 



Art. I. — Young Stages of Dicksonia and Cyathea, 

 By G. B. Stephenson, M.Sc. 



[Read before the Manawatu Philosophical Society, 20th June, 1907. J 



Plates I-V. 



Introduction. 



Of late vears it has been recognised that anatomical relations 

 that are not directly dependent on the mode of life of the plant 

 often indicate with some certainty community of descent. But 

 Bower (Phil. Trans., 1900), in his work on the leptosporangiate 

 ferns, practically omits anatomical structure from considera- 

 tion. He points out affinities from the character of the sorus. 

 But it was hoped, in the present work, that a study of the early 

 stages of the different genera of tree-ferns would show that 

 their community of descent was shown by similarity of struc- 

 ture ; and especially that the method of attaining a tubular 

 stele from a solid strand would show distinct constant cha- 

 racters. But it has been found that there is a striking similarity 

 in the early stages of all the modern feins investigated. Spore- 

 lings of Lomaria, Hypolepis, Doodia> Asplenium, Polypodvum.' 

 punetatum, Pteris incisa, all show a similar stelar structure to 

 the tree-fern sporelings. It is only when the tubular stele begins 

 to break up that marked distinctions appear. Probably in the 

 great group of more modern ferns there is great variability 

 even in the early stages of the sporophyte and the attainment 

 of similar structure by plants only remotely related in the group- 

 In connection with this study, cultures of the prothallia of 

 Dicksonia squarrosa and three Cyatheas — dealbata, medullaris, and 

 Cunninghamii — were grown. The prothallia and the young spor- 

 ophytes were imbedded in paraffin, cut with the microtome, and 

 stained on the slide. The work was carried on in the laboratory 

 of the Auckland University College, and the writer will always 

 recognise a heavy debt of gratitude to Professor H. P. W. Thomas. 

 1— Trans. 



