298 



MARTIN BORRILL 



For many specimens the diagnostic key given by Tutin (1952), taken in relation 

 to the general habit, vegetative and floral characters of the plant, will be found satisfactory. 

 The following key has been devised taking into account the extreme variants found 

 in this group. To identify G. X pedicellata the culms should be young enough to contain 

 anthers, or old enough for the persistent nature of the spikelets to become apparent. 

 In the other species the diagnostic value of the epidermal cell character deserves emphasis. 



Identification Key for Critical Specimens of Section Glyceria. 



1. Plants sterile, anthers shrunken and x-shaped, pollen empt>'; or empty, persistent spikelets on 

 mature culms. 2 

 Plants fertile, anthers normal, pollen full, or seed present and spikelets breaking up on mature 

 culms 4 



2. Lemmas mostly exceeding 5*0 mm, anthers mostly over 1-2 mm G. X pedicellata 

 Lemmas 4-5 to 5-0 mm., anthers less than 1-2 mm. 3 



3. Irregular pairing at meiosis, many univalents present G. X pedicellata 

 Complete pairing at meiosis, sometimes multivalents present G. plicata forma 



4. Lemmas 5-25 to 7-25 mm., with apices acute or obtuse, anthers 1-75 to 2-75 mm.; nen/es of sheath 

 towards blade smooth, caryopses oblong-elliptic 2-5-3-0 mm. G. fiuitans 

 Lemmas 3-5 to 5-25 mm., with apices rounded, lobed, or 3- to 5- toothed 5 



5. Lemma apex 3- to 5-toothed, sometimes obscurely or markedly three-lobed, nerves and surface 

 minutely scaberulous ; sheath nerves towards blade with inflated cells, these each having a minute 

 lateral tooth, caryopses oblong - elliptic, 1 •5-2-0 mm. G. declinata 

 Lemma apex rounded, or obscurely, rarely markedly, three-lobed, surface scabrid on nerves only ; 

 sheath nerves towards blade very scabrid, with numerous minute rough points; car^^opses obovate, 

 1 •5-2-5 mm. G. plicata. 



Acknowledgments 



My thanks are due to Professor T. G. Tutin, who directed these studies, to Mr. C. E. 

 Hubbard and Dr. J. M. Lambert; to those in charge of the herbaria at Kew, the British 

 Museum (Nat. Hist.), and Cambridge, for making available material for study; to the 

 Director of the Welsh Plant Breeding Station and Mr. A. R. Beddows for providing 

 facilities for writing up the results, and to colleagues both at Leicester and Aberystwyth. 



REFERENCES 



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