COMPARATIVE STUDY OF DIPLOID AND TETRAPLOID SPORES OF 

 DRYOPTERIS DILATATA FROM BRITAIN AND EUROPE* 



By Fern Ward Crane 

 Summit, New Jersey 



It has been noted that spore characters are diagnostic for separating various North 

 American taxa of Dryopteris (Crane, 1953). Professor Irene Manton {see Manton, 1950), 

 University of Leeds, and Dr. Stanley Walker, University of Liverpool, who have worked 

 on the cytology of diploid and tetraploid specimens of British and European D. dilatata 

 (Hoffm.) A. Gray, report it difficult to distinguish the fronds on the basis of gross mor- 

 phological characters. In a recent conference. Professor Manton asked me to describe 

 spores of such specimens in order to ascertain any correlation. 



Mature spores of Dryopteris are protected by an alate membrane or perispore (Bower, 

 1928). In the " spinulosa " complex this perispore is spinose, the size and spacing of 

 spinules varying with the taxon. Since there is no appreciable difference between these 

 spores whether collected from living plants or herbarium specimens, I make comparative 

 studies from the dried fronds. Another factor, a proper mounting medium, insures the 

 stability of material to be examined. Permount, a synthetic resin solution, is most 

 suitable for preparing permanent slides. This medium does not cause shrinking or 

 swelling of the spores, but it preserves them naturally and permanently. 



The accompanying figures of typical diploid and tetraploid spores of D. dilatata 

 were originally plotted on graph paper according to measurement. Diploid specimens, 

 collected in Scotland, Sweden, and Switzerland, and tetraploid plants gathered in England, 

 Ireland, and Sweden, were made available. 



There proved to be surprising dissimilarities between spores of diploid and tetraploid 

 specimens of D. dilatata. While the sizes are not particularly indicative, an obvious 

 difference in texture can be observed at first glance, even under low magnification. The 

 spore of the diploid has a thin, tan-coloured, membranous perispore; in that of the 

 tetraploid this structure is heavy, dark brown, and coriaceous. 



A measurable difference in spinule size and spacing on the perispore of the two 

 types is another constant criterion of discrimination. In a spore of the diploid the spinules 

 are minute, blunt-tipped, 1 /x or less in height, and more or less widely spaced on the 

 surface of the perispore. The spinules of a tetraploid specimen are large, heav\^ coarse, 

 thick-set, blunt-tipped, irregular, up to 2 /x, and crowded. 



Thus it may be concluded from the above observations that spore characters are 

 diagnostic for the diploid and tetraploid D. dilatata under consideration. 



It is possible that a similar situation occurs in D. spinulosa of North America, and 

 this problem is being studied in collaboration with Manton & Walker (1953). 



• This study is financed in part by a grant-in-aid from the American Philosophical Society. 



REFERENCES 



BOWER, F. O., 1928, The Ferns (FiUcales), 3, 125. Cambridge. 



CRANE, FERN WARD, 1953, Spore Studies in Dryopteris, I, Amer. Fern Jour., 43, 159-169. 

 MANTON, IRENE, 1950, Problems of Cytology and Evolution in the Pteridophyta, p. 75. Cambridge. 

 MANTON, IRENE & WALKER, STANLEY, 1953, Cytology of the Dryopteris spinulosa complex in 

 Eastern North America, Nature, 171, 1116. 



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