296 



MARTIN BORRILL 



are in Babington's Herbarium at Cambridge including a duplicate of the type. The follow- 

 ing morphological notes were made from specimens of Townsend's which have been 

 examined. 



Morphological Notes : — Townsends' specimens of G. X pedicellata in Herb. Babington 



at Cambridge. 



Fulbourn Ditch, Cambs. May, 1846 Anthers 1-0-2' 20 mm., completely sterile. Sub- 

 - as (MS) Glyceria hybrida. F.T. basal lemmas 4-5-5-0 mm., scaberulous 

 Sheet 106 (Sheet 108 Duplicate). on nerves and to some extent on general 



surface. Lemma apices lobed and rather 

 truncate, as in G. plicata. Leaf sheaths 

 slightly scabrid on ribs towards blade. 



There is a specimen of G. plicata on this sheet, lemmas 4-0-4-3 mm., anthers 1-0- 

 1-3 mm. Fertile. 



Wood Ditton, Cambs. 27/5/1848. 

 -as (MS) G. hyhrida Towns. Sheet 

 407. 



Anthers 1-5-1 -75 mm., completely sterile. Sub- 

 basal lemmas 5 -0-5 -75 mm., highly scabrid on 

 nerves and on general surface. Lemma 

 apices obtuse. Leaf sheaths highly scabrid on 

 nerves and approaching plicata type. 



The specimens on sheets 106 and 407 in Herb. Babington are so different that the 

 range of variation in lemma and anther length does not appreciably overlap. Townsend's 

 description refers to the form with short lemmas. The epidermal character of the lemmas 

 is of the G. plicata type, this is made clear by the passage italicised by me in Townsend's 

 description. It is nevertheless apparent that Townsend recognised the great variability 

 of the hybrid and included in his collections specimens varying in intermadiacy between 

 the parents. 



Some specimens named G. X pedicellata are met with, which are indistinguishable 

 from G. plicata except that they are pollen- sterile. Amongst these one may include the 

 duplicate of Townsend's type specimen in Herb. Babington, the description and mor- 

 phology of which would equally well fit G. plicata. Similar specimens have been seen 

 in Herb. Kew (CEH 12744) and in Herb. British Museum. 



The range of variation exhibited by G. X pedicellata overlaps that of the parent species 

 to an extent which suggests that the hybrid is polytopic in origin, involving infrequent 

 crosses between plants from different parts of the variable populations of the parental 

 species. 



Sterile G. plicata 



Sterile plants morphologically indistinguishable from G. plicata are not often met 

 with in the field; however, after much searching, a clone was discovered at Empingham 

 Marsh, v.c. 55 (H.426*). The diagnostic features of this plant are : — 



Lemmas short, 3-75 to 4-75 mm., apices rounded, scabrid on the nerves only; anthers 

 0-9 to 1-15 mm., indehiscent, pollen sterile; no seed produced, spikelets persistent. Nerves 

 of leaf-sheath towards blade highly scabrid, of plicata type (Table 1. q.v.). The results 

 of cytological studies (to be given in a second paper) strongly suggest that this plant is a 

 form of G. plicata. The morphology of typical spikelets of species of the section Glyceria 

 is illustrated in Plate 20, enabling a comparison to be made between H. 426 (sterile G. plicata), 

 Townsend's short and long lemma forms, " typical " G. X pedicellata, and the fertile 



• Specimen citation given in the following abbreviated form : H.426 = specimen No. 54426 in Herb. University College 

 Leicester. 



