THE POLYPLOID SERIES IN OSMUNDA 



on and subdivided. The triploid prothallial culture so obtained is now about 6 years 

 old. It has not yet produced a young plant, but it is perhaps still possible that in time 

 it may do so. The parent plant has been allowed to return to normal. 



a be 



Fig. 14. Comparative leaves from the polyploid series of Osmunda; terminal leaflets from sterile fronds 

 of comparable stature, a, diploid; b, triploid; c, tetraploid. The triploid shows gigantism, but the 

 tetraploid is depauperate and also abnormal in shape. Half natural size. 



a b c d 



Fig. 15. The polyploid prothalli of Osmunda. Natural size, photographed at the end of the growing 

 season, in autumn, a, b and d photographed at the same time under strictly comparable conditions ; 

 c from a different year, a, haploid; b, diploid; c, triploid; d, tetraploid. The diploid and triploid 

 both seem to show gigantism, but the tetraploid is small and abnormally indented at the edge. 

 Triploid and tetraploid are unable to reproduce, but haploid and diploid are very fertile. 



While there is still some chance that the series may be extended in the future should 

 either of the high-numbered prothalli become fertile, until they do so further progress is 

 blocked. We must therefore be content with diploid, triploid and tetraploid sporo- 

 phytes and haploid, diploid, triploid and tetraploid gametophytes. 



29 



