210 PLANT-LIFE 



gate is a unit composed of heterogeneous parts, and so 

 is the plant kingdom. Ancient and modern, simple 

 and complex, lower and higher, regenerate and degener- 

 ate, are all parts of the great whole. They occur side by 

 side, but their very proximity, to the trained eye, serves 

 to show their distinctions. In both the Choripetalse 

 and the Sympetalse there are plants that may be termed 

 " lower," " higher," and " highest," and there are also 

 gradationary forms connecting the groups. 



The AmerMcece, which usually bear single flowers 

 arranged in catkins, and are generally pollinated by 

 wind, are considered to be the lowest of the Choripetala?. 

 They are mostly trees or shrubs; the flowers are uni- 

 sexual, inconspicuous. They are either destitute of a 

 perianth, or in species where it is present it consists of 

 a single whorl, is never brightly coloured, but always 

 reduced to inconspicuous scales. It is frequently argued 

 that the inflorescence of these catkinate plants is a reduc- 

 tion from a more advanced ancestry; but this need not 

 be admitted, especially as there is some geological 

 evidence in favour of their being primitive among 

 Dicotyledons. The Amentaceae include the Willows, 

 Poplars, Oaks, Birches, Alder, and Hazels. In the 

 Willows (Salicince) the sexes are represented on separate 

 plants, the male and female flowers occurring in simple 

 catkins. In Britain the most important species are the 

 Crack Willow (Salix fragilis), the Weeping Willow 

 (S. Babylonica), the Osier (S. viminalis), and the Sallow 

 or Goat Willow (S. Caprea). The last-named species is 

 the source of the so-called " palms " gathered by children 

 for Palm Sunday. The " palms " are the catkins, which 

 appear before the leaves. The Sallow is pollinated by 



