40 THE BOOK OF NATURE STUDY 



as possible ; a gravelly loam is the best soil ; loose sandy loam, 

 pure clay and peaty soils are to be avoided. The Cress is 

 propagated by division of the plants : this is done between 

 hay -making and harvest, and is continued until the end of 

 October. The top of the plant is cut out, the length of the 

 cutting averaging one foot, but this varies according to the depth 

 of the water. Some growers cultivate stocks for planting in 

 smaller streams isolated from the main bed, in order to get 

 more robust plants. The beds should be thoroughly cleaned 

 out and replanted each season. The growing of Water-Cress is 

 not a very remunerative industry, but it does give employment 

 during the great part of the year to those engaged in it. 



The presence of a stream has great influence on the vegetation 

 of the adjoining hedge. A country lane with a stream along the 

 lower hedges, woods bordering its upper end and pastures beyond, 

 will afford at least three types of vegetation. The hedges by 

 running water will luxuriate in such plants as the Rosebay Willow- 

 Herb, the Hemp Agrimony, the Purple Loosestrife, and the 

 Meadow-sweet ; while underneath, in the shade afforded by them 

 and at the edge of the water, will be found the Golden Saxifrage 

 and a species of Bitter Cress (Cardamine flexuosa). The Willow- 

 Herbs are a large genus, and have been thus named from the re- 

 semblance of their leaves to those of the Willow, which is often 

 associated with it on the banks of streams. The Rosebay is one 

 of the largest species, reaching even four feet in height ; unlike 

 many of the other species, it is not hairy. The flowers are purplish- 

 red and very showy, and the stigma is deeply four-lobed. In 

 identifying the different species of Willow- Herbs, one of the first 

 things to examine is the stigma ; some have a four-lobed stigma, 

 others a club-shaped one. This plant is very much visited by 

 insects, and as the stamens mature before the ovules, cross- 

 pollination usually takes place. 



The Purple Loosestrife (Lythrum Salicaria) has long spikes 

 of rose-coloured flowers, which are very interesting, for there are 

 three types of these flowers. Each has two sets of stamens, 

 the position of which varies with regard to the stigma. The 

 style is also of different length. In one type it is short, and 

 the two rows of stamens, six in each row, are then above the 



