Page:Aspects of nature in different lands and different climates; with scientific elucidations (IA b29329668 0002).pdf/340

 from 1800 to 2000 years. The root of the rose tree growing against the crypt of the Cathedral of Hildesheim is 800 years old. A kind of sea-weed, Macrocystis pyrifera, attains a length of 630 English feet, exceeding therefore the height of the loftiest Coniferæ, even that of the Sequoia gigantea     94-97

Examination of the probable number of phænogamous plants hitherto described or preserved in herbariums. Relative numbers. Laws discovered in the geographical distribution of plants. Relative numbers of the great divisions of Cryptogamia to Cotyledonous plants, and of Monocotyledonous to Dicotyledonous plants, in the torrid, temperate, and frigid zones. Elements of arithmetical botany. Number of individuals; predominance of social plants. The forms of organic beings are mutually dependent on and limit each other. If we know exactly the number of species of one of the great families of Glumaceæ, Leguminosæ, or Compositæ, at any one part of the globe, we may infer approximatively both the number of species in the remaining families, and the entire number of phænogamous plants in the same district. Application of the numerical ratios to the direction of the isothermal lines. Mysterious original distribution of types. Absence of Roses in the southern, and of Calceolarias in the northern hemisphere. Why has our heather (Calluna vulgaris), and why have our oaks never advanced eastward beyond the Ural Mountains into Asia? The vegetation cycle of each species requires for its successful organic development a certain minimum amount of temperature. 97-113

Analogy between the numerical laws of the distribution of animal and of vegetable forms. If there are now cultivated in Europe above 35000 species of phænogamous plants, and if our herbariums probably contain, described and undescribed, from 160000 to 212000 species of phænogamous plants, it is probable that the number of collected insects and collected phænogamous plants are nearly