11 CKUCIFEll^ 79 



tion more difficult. The insect visitors are bees, Hies, 

 and beetles. The pods are oblong and turgid. 



In N. silvestre the nectaries do not meet, but form 

 four fleshy glands. The pods are linear, and more or 

 less curved ; the seeds are rather less numerous. Why 

 should two plants so similar and so nearly allied have 

 such different pods ? 



Cardamine 



0. pratensis (Cuckoo-flower). — The flowers are larger 

 than in most of its allies, aijd more visited by insects. 

 There are four nectaries — two at the bases of the two 

 shorter stamens, and two smaller ones at the base of the 

 two longer ones. The honey collects at the bowed base 

 of the sepals. The pouches of the two sepals correspond- 

 ing to the larger nectaries are more roomy than the 

 others. The yellow anthers make a quarter turn when 

 opening. On the contrary, in the case of the two short 

 stamens the anthers open inwards. According to Hilde- 

 brand, the plant is self-sterile. In addition to bees, 

 flies, and beetles, the flowers are visited occasionally by 

 butterflies and hawkmoths. 



C. amara (Bitter Cress) agrees in many respects with 

 C pratensis, but the anthers are purple. 



C. hirsuta is a common weed in gardens, with erect 

 stems about a foot high. The leaves are pinnate, the 

 flowers small and white ; the petals are sometimes absent. 

 The name is far from appropriate, as the plant is almost 

 glabrous, having only a few scattered hairs. Though the 

 flowers are so small, they are not entirely deprived of 

 insect visits, in the absence of which, however, as the 

 anthers are close to the stigma, the plant fertilises 

 itself The inner layers of cells of the walls of the pod 

 gradually come to a condition of great tension, so that 

 when ripe the walls of the pod detach themselves at the 

 slightest touch from below upwards, fly off" elastically, 

 and scatter the seeds. In this country it is annual, but 

 plants grown by Kerner in his Alpine garden became 

 perennial. The same change occurred in various other 



