592 GRAMINACEAE 



Hep. of Bot. Exch. Club, 1888. Wytham, ihe author, I. c, 1892. 

 Plentiful in most of the Thames meadows, as at Lechlade, 

 Buscot, Radcot, Appleton, Longworth, Cumnor, &c. 



2. Ock. Marcham. Hinksey. Radley. Frilford. Blewburton. 



Upton. Shippon. Ufiington. 



3. Pang. Moulsford. Basildon. 



4. Kennet. Aldermaston. West Ilsley. Bagnor. Inkpen. Hunger- 



ford. Kintbury. 



5. Loddon. On the Reading road near Hurst, Melvill. Fineh- 



ampstead. Jouldern's Ford. Sonning. Bisham. Bray. Windsor. 



Although I have kept B. racemosus and B. commutatus as distinct species, 

 I have no doubt that they are merely forms of one polymorphic plant, which 

 might he better expressed by considering B. commutatus as a var. of B. race- 

 mosus. With reference to this opinion, I may quote from a letter which 

 Professor Hackel, of St. Poelton, wrote me in 1894 : ' I paid particular attention 

 to the forms of B. racemosus and B. commutatus from the neighbourhood of 

 Oxford, of which you WTite that you are at a loss to distinguish them. 

 I must confess that I also have altered my opinion on the value of the 

 distinctive characters of the two species. I am now inclined to see in them 

 only varieties of one species, which is to bear the older name of B. racemosus. 

 The intermediates between the two plants are too numerous, the differences 

 too weak, as to be equal to those between good species. Some of the 

 characters, as for example the outlines of the flowering glumes seen from 

 aside, are almost illusive, because they do not coincide with those of the 

 form of panicle.' Prof. Hackel kindly drew up the following diagnosis of 

 the two plants : — 



' B. racemosus, Linn. var. genuinus : panicle short, after flowering erect, 

 inferior branches no more than one-third the length of the panicle. Spikelets 

 almost ovate or ovate-lanceolate, measuring from the base to the apex of the 

 sixth flower not more than 12-13 mm., anthers 2-2-5 mm. long. 



'Var. COMMUTATUS : panicle, in typical specimens, after flowering drooping, 

 much longer ; the inferior branches about one-half of the length of the 

 panicle. Spikelets lanceolate or ovate-lanceolate, measuring from the base 

 to the apex of sixth flower 15-16 mm., anthers 1-5, rarely 2 mm. long.' 



B. commutatus, although often found in the rich meadows of the 

 Thames and its tributaries, in which B. racemosus also occurs, is 

 almost exclusively the plant of cornfields, in which I do not remember 

 to have seen B. racemosus. 



B. commutatus offers a wide range of forms, irrespective of the inter- 

 mediates, with JS. racemosus. An extreme form is one with very 

 compound panicle, in which the individual spikelets are considerably 

 larger than in the ordinary form, and contain eight or more florets = 

 the var. multifloeus, Parnell, 1. c. 274 ; this I have seen from the 

 Thames meadows and from Moulsford. Var. pubescetis, a form in 

 which the spikelets are slightly pubescent, also occurs, as at Hinksey, 

 Cumnor, Blewbury, Benham, Twyford, &c. 



A form was gathered near Oxford in which the rigid panicle branches 

 were divaricate, and plants with purplish glumes are also found. 



Prof. Hackel kindly gave me the means of distinguishing B. secalinus from 



