THE ANCIENT FERNS 



Cruciferae and some other numbers can be found. In the Pteridophyta such low num- 

 bers have very rarely been encountered, but instead we find polyploid series on 37 or 41, 

 prime numbers which cannot possibly be primitive. Only in the microphyllous groups, 

 though in most of these indirectly, are we sometimes led to consider 9 or 10 or their 

 multiples. In the ancient ferns, however, there are signs of these numbers again. 

 Ophioglossum, as we have seen, may be polyploid on 8, Hymenophjllum and Trichomanes bear 

 a quite definite relation to 9, and the Osmundaceae are similarly related to either 1 1 or 

 22 as the case may be. The importance of these groups lies at least as much in this fact 

 as in the interest which they excite for their own sakes. No matter how imperfectly, 

 they demonstrate with sufficient clearness that even the Pteridophyta must have started 

 life in the distant past from cytologically simple beginnings. And before a general 

 interpretation of our data can be even attempted this is a fact which we very much need 

 to know. 



SUMMARY 



The Ophioglossaceae, Hymenophyllaceae and Osmundaceae have been examined, the 

 first two in their British representatives only, and the last also from botanic gardens. 

 Ophioglossum is remarkable as the highest chromosome number yet recorded in the plant 

 kingdom. Hymenophyllum is remarkable for having the largest chromosomes in the ferns 

 and the lowest chromosome number known in the group. The Osmundaceae stand out 

 as the only group which seems to be genuinely primitive in all respects. 



2n 



List of new chromosome numbers introduced in the chapter 



Ophioglossaceae 



Ophioglossum lusitanicum L. 



0. vulgatum L. 



Botrychium lunaria (L.) Sw. 



Hymenophyllaceae 



Trichomanes radicans Sw. 

 Hymenophyllum unilaterale Bory 

 H. tunbridgense (L.) Sm. 



Osmundaceae 



Osmunda regalis L. (Chapter 3) 



0. cinnamomea L. 



0. Claytoniana L. 



0. gracilis Hort. 



O. palustris Hort. 



O. javanica Bl. 



Todea barbara (L.) Moore 



Leptopteris Frazeri (Hk. et Grev.) Presl 



L. hymenophylloides (A. Rich.) Presl 



L. superba (Col.) Presl 



280 



