88 BRITISH FLOWERING PLANTS chap. 



ditions supposed by some to be due to cold, as the 

 hermaphrodite plants are said to come on later in the 

 season. Warnstorf also remarks that in the earlier 

 flowers the stamens are often incomplete. 



Lepidixjm 



From X67rt9, a scale, in allusion to the flattened pods. 

 The outer layer of the seed-coat contains a mucilaginous 

 adhesive substance which rapidly absorbs moisture and 

 serves to fix them as soon as they are brought into 

 contact with damp earth. 



L. Draba has six small, green nectaries between the 

 bases of the six stamens. The anthers open inwards, 

 but the stamens bend outwards, thus for the time check- 

 ing self-fertilisation. Insects, therefore, turn different 

 sides of their body to the stamens and the stigma, thus 

 favouring cross -fertilisation. Subsequently the parts 

 close up, so that in the absence of insects the flower 

 fertilises itself The plant is slightly protogynous. 

 The longer stamens at first place themselves behind the 

 petals, so that insects do not touch them, and after 

 a while move inwards so as to touch and fertilise the 

 stigma. The pollen of the shorter stamens, on the 

 contrary, serves entirely for cross-fertilisation. The 

 plant is a native of South - Eastern Europe and 

 Western Asia, which has been introduced or become 

 established in many places in fields, banks, and railway 

 cuttings. 



L. sativum (Cress) has four nectaries. While the true 

 British species of Lepidium have entire cotyledons, in 

 the Cress they are divided into three long narrow lobes 

 (Fig. 48). I have suggested the following reason for 

 this in my book on seedlings.-' 



Fig. 49 represents a section through the seed of 

 L. graminifolium, which may be taken as representing 

 the ordinary arrangement in the genus. The seeds, 

 conforming to the shape of the capsule, are somewhat 

 triangular, with the radicle in the narrow end. The 



' On Seedlings, vol. i. 



