134 BRITISH FLOWERING PLANTS chap. 



be pressed downwards, and, as M. Eoux has shown, this 

 mechanism thus serves actually to bury the seed. His 

 observations were made on an allied species, Erodiuvi 

 ciconium, which he chose on account of its size. He 

 found that if a seed of this plant is laid on the ground 

 it remains quiet as long as it is dry, but as soon as it is 

 moistened — i.e. as soon as the earth becomes in a con- 

 dition to permit growth — the outer side of the awn 

 contracts, and the hairs surrounding the seed commence 

 to move outwards, the result of which is gradually to 

 raise the seed into an upright position with its point 

 on the soil. The awn then begins to unroll and con- 

 sequently to elongate upwards, and he suggests that, as 

 it is covered with reversed hairs, it will probably press 

 against some blade of grass or other obstacle, which will 

 prevent its moving up, and will therefore tend to drive 

 the seed into the ground. If, then, the air becomes 

 drier the awn will again roll up, in which action M. 

 Eoux thought it would tend to draw up the seed ; but 

 from the position of the hairs the feathery awn can 

 easily slip downwards, and would therefore not affect 

 the seed. When moistened once more it would again 

 force the seed further downwards, and so on until the 

 proper depth was obtained. 



E. cicutarium is sometimes nearly glabrous, some- 

 times has glandular hairs ; and in E. moschatum glan- 

 dular hairs are always present, giving the plant a strong 

 odour of musk, whence it derives its specific name. In 

 E. maritimum the hairs are soft and often glandular. 



OXALIS 



Of this genus we have two species — 0. Acetosella 

 with white, 0. corniculata with yellow flowers. Some 

 of the foreign species are trimorphic (see Primrose and 

 Lythrum), some dimorphic, others, including the two 

 British, monomorphic. 



0. Acetosella (Wood-sorrel). — This is one of the plants 

 regarded as the Shamrock. The leaves have a pleasant 



