^CYTOGENETIC STUDIES 

 IN THE DRYOPTERIS SPINULOSA COMPLEX - 1 



By S. Walker 



The Hartley Botanical Laboratories, University of Liverpool 



Abstract 



The inter-relationships of species within the Dryopteris spinulosa complex have 

 been studied by investigating chromosome pairing during meiosis in wild and synthesised 

 hybrids. 



The three tetraploid species D. cristata', D. spinulosa and D. dilatata are shown to 

 be allopolyploids requiring at least four ancestral diploids to account for their origin. 

 Experimental hybridisations indicate that one of these ancestral genomes is now repre- 

 sented by two distinct diploid forms. 



Table of Contents 



(1) Introduction 



(2) Materials 



(3) Methods 



(4) Survey of previous work 



(5) Experimental : 



(A) Hybrids of wild origin 



(B) Synthesised hybrids 



(6) Discussion 



(7) Summary 



(8) Acknowledgments 



(1) Introduction 



A cytogenetic and taxonomic investigation of the Dryopteris spinulosa complex, as 

 found in Europe and North America, is helping to elucidate the relationships between 

 members of this circumboreal group of ferns. This paper is devoted entirely to the 

 D. spinulosa complex in Europe. A report on the complex in N. America is being pre- 

 pared, whilst further work, inter-relating species on both sides of the Atlantic, is in 

 progress. 



The D. spinulosa complex has long been a source of confusion for taxonomists. In 

 modern Floras it is represented by three distinct species and the hybrids between them. 

 The nomenclature varies somewhat but following Christensen (1905, 1913) they may 

 be listed : 



(i) Dryopteris cristata (L.) A. Gray, 



(ii) Dryopteris spinulosa (O. F. Muell.) Watt, 



(iii) Dryopteris dilatata (Hoffm.) A. Gray, 



(iv) Hybrid, D. X uliginosa (Newm.) Druce (= D. cristata X spinulosa), 



(v) Hybrid, D. dilatata X spinulosa. 



* Part of a thesis approved for the degree of Ph.D. by the University of Leeds. 



193 



