BIOSYSTEMATIC STUDY OF SOME GLYCERIA SPECIES -I 



297 



320 



35 39 43 47 51 55 59 63 



Grain diameter (Classes of 4 fi) 



Fig. 2. Pollen diameter in three species of Glyceria. Grain diameter (classes of 4 ft). Means : 1. G. declinata 

 41-1 /i. 2. G. fluitans 42-1 /i. 3. G. plicata 48-3 /x. Difference between 1 and 3 significant at P = 0-05. 



species. Plate 19 shows pollen of H.426, G. Xpedicellata, and for comparison of fertility. 

 G. plicata also. The pollen of G. declinata, G. plicata and G. fluitans is highly fertile, 

 That of G. X pedicellata and H.426 is highly sterile. 



Conclusion 



It is apparent that, in the absence of cytological evidence, some sterile specimens of 

 section Glyceria will be difficult to identify, involving a chance of error. This applies to 

 the particular plant described by Townsend, which may in fact be a form of G. plicata. 



Difficulties in identification are due to : — 



1. The intrinsic variability of the species, which results in overlapping ranges of varia- 



tion in quantitative and qualitative morphological characters. 



2. The presence of the very variable hybrid between G. fluitans and G. plicata. 



3. The occasional occurrence of sterile clones of G. plicata. 



