SUMMARY. PHTSIOUWOMT OF PLANTS. XXVlI 



Europe, and if from 160,000 to 212,000 phanerogamia are now con- 

 tained, described and undescribed, in our herbariums ; it Is probable 

 that the number of collected insects scarcely equals that number of 

 phanerogamia; whereas in individual European districts the insects 

 collected preponderate in a threefold ratio over the phanerogamia 

 pp. 287-291. 



Considerations on the proportion borne by the number of the phane- 

 rogamia actually ascertained, to the entire number existing on the 

 globe pp. 291-295. 



Influence of the pressure of atmospheric strata on the form and life 

 of plants, with reference to Alpine vegetation pp. 295-296. 



Specialities on the plant-forms already enumerated. Physiognomy 

 of plants discussed from three different points of view: the absolute 

 difference of the forms, their local preponderance in the sum total 

 of the phanerogamic Floras, and their geographical as well as climatic 

 dispersion pp. 296-346. Greatest height of arboral plants; examples 

 of 223 to 246 feet in Pinus Lambertiana and P. Douglasii, of 266 in P. 

 Strobus, of 300 feet in Sequoia gigantea and Pinus trigona. All these 

 examples are from the north-western part of the New Continent. The 

 Araucaria excelsa of Norfolk Island, accurately measured, rises only 

 from 182 to 223 feet; the Alpine palms of the Cordilleras (Ceroxylon 

 andicola), only 190 feet pp. 322-324. A contrast to these gigantic 

 vegetable forms, presented not merely by the stem of the arctic willow 

 (Salix arctica, two inches in height,) stunted by cold and exposure on 

 the mountains, but also in the tropical plains by the Tristicha hypnoides, 

 a phanerogamic plant which is hardly three French lines (quarter of an 

 inch) in height, when fully developed pp. 324-325. 



Bursting forth of blossoms from the rough bark of the Crescentia 

 Cujete, of the Gustavia augusta, from the roots of the Cacao tree. The 

 largest blossoms borne by the Eafflesia Arnoldi, Aristolochia cordata, 

 Magnolia, Helianthus annuus p. 348. 



The different forms of plants determine the scenic character of vege- 

 tation in the different zones. Physiognomic classification, or distribu- 

 tion of the groups according to external facies, is from its basis of 

 arrangement entirely different from the classification according to the 

 system of natural families. The physiognomy of plants is based 

 principally on the so-called organs of vegetation, on which the preser- 

 vation of the individual depends ; systematic botany bases the classifi- 

 cation of the natural families on the consideration of the organs of 

 reproduction, on which the preservation of the species depends 

 pp. 348-352. 



ON THE STRUCTURE AND MODE OF ACTION OF VOLCANOS 



IN DIFFERENT PARTS OF THE EARTH pp. 353-375. 

 Influence of travels in distant lands on the generalization of our ideas 

 end on the progress of physical orology. Influence of the conformation 

 &f the Mediterranean on the earliest ideas respecting volcanic pheno- 



