25 2 Ward. — On Relations between Host and Parasite 
it is difficult to detect any difference beyond size. The four- 
day seedlings are like those of the last species. In a week 
the first leaf-spear is 1-2 mm. above ground, and in a pot 
five days in the intermediate pit only two spears showed, 
about 5 mm. high. B. racemosus , L., is a common European 
plant, and regarded by Bentham as merely a smoother variety 
of B. arvensis. But we must bear in mind the extensive 
definition of the latter species given by Bentham. The more 
usual view is to regard it as a good species 1 . 
B. commutatus. 
Is quite like B. racemosus , of which it is often regarded as 
a variety. The ‘seed* measures 10 x 2 mm. with an awn 
the same length. The colour may be a trifle paler in the 
mass, but there are no marked points of difference to be seized. 
The seedlings of B. commutatus are also very like those 
of B. racemosus. In a week the spears were 2-3 mm. high, 
and in the intermediate pit the tips only just showed in five 
days. 
In a fortnight the total height was about 8 cm. The leaf 
averaged 6 cm. x 2 mm. and had seven ribs ; the cilia, hairs, 
ridges, &c., were like B. arvensis , and the sheath almost 
smooth. 
B. commutatus resembles also B . mollis in four-day seed- 
lings, but is far behind it in rapidity of germination, 
B. commutatus , Schrad., is synonymous with B. racemosus 
according to the Index Kewensis , cf. FI. Germ., i. 353. In the 
London Catalogue, 9th ed., 1895, p. 44, it is accorded specific 
rank 2 , however, with two varieties. 
B. secalinus , L. 
Next in point and size comes B. secalinus , which is rounded 
and fatter and more bulky and corn-shaped than any of the 
foregoing. Length 7 mm., breadth 2 mm., and thickness 
about the same. Awn 5-6 mm. In the mass the c seed ’ is 
distinctly heavier : in colour it is grey-yellow like B. mollis. 
1 Lond. Cat., ninth ed., 1895, p. 44. 
2 See also Ascherson, 1 . c., p. 613. 
