ZONES OF MAEIJTE VEaETATION. 699 



3. Eegion of Myrtaces and Lauraceffi, extending from 3800 to 6700 feet. (Sub- 



tropical zone.) 



4. Eegion of Evergreen Dicotyledonous trees, extending from 5700 to 7600 feet. 



(Warm Temperate zone. ) 



5. Eegion of Deciduous Dicotyledonous trees, extending from 7900 to 9500 feet. 



(Cool Temperate zone.) This ief not always well marked in the Tropical and 

 Equatorial zones, owing to want of sun and deficiency in moisture. 



6. Eegion of Coniferse, the Pine and Fir, extending from 9500 to 11,400 feet. 



(Sub-arctic zone. ) On the Cordilleras of the Andes this zone is marked by 

 Escallonias. On the Soandinaviau mountains and the Himalaya, Birches also 

 occur. 



7. Eegion of Alpine Shrubs or of Ehododendrons, extending from 11,400 to 



13,300 feet. (Arctic zone.) On the Andes the .zone is characterised by 

 Bejarias, and on the Himalaya by Willows, Junipers, and species of Eibes. 



8. Eegion of Alpine Plants and Lichens, extending from the upper limit of shrubs 



to the snow-line at 15, 200,feet. (Polar zone.) Lichens abound in this region. 

 The Alpine herbs are mostly perennial. They are protected during winter 

 by a covering of snow. Their flowers are often large and beautiful. 



Zones of Marine Vegetation. 



The ocean, as well as the land, possesses its vegetable forms, 

 which vary according to their position, surrounding medium, relative 

 degrees of pressure, and exposure to light. Harvey has observed that 

 some seaweeds seem to be unaffected by circumstances of this nature, 

 and are found equally abundant under opposed latitudes and in 

 extremes of temperature. The lower we descend in the scale of marine 

 vegetation the better is this illustrated. Some seaweeds, Harvey 

 remarks, are cosmopolitan or pelagic, as species of Ulva and Entero- 

 morpha, which are equally abundant in high northern and southern 

 latitudes, as they are under the equator and in temperate regions. 

 Oodium tomentosum, Oeramium rubrum, 0. diaphanum, species of 

 Ectocarpus, and severar Confervse, have a range nearly as wide. Plo- 

 camium coccineum and Gelidium corneum are common to the Atlantic 

 and Pacific oceans; Khodymenia palmata, the common Dulse of 

 Britain, is found at the Falkland Islands and Tasmania. Fucus 

 tuberculatus extends from Ireland to the Cape of Good Hope ; Fucus 

 vesiculosus occurs on the north-west coasts of America, and on the 

 shores of Europe ; whUe Desmarestia ligulata is found in the north 

 Atlantic and PaciJ&c oceans, as well as at the Cape of Good Hope and 

 Cape Horn. Many Diatomaceee are distributed from pole to pole, 

 and are found in the lowest depths of the ocean. In the antarctic ocean. 

 Hooker found Diatoms constituting a bank which stretched 200 miles 

 north from the base of Victoria Barrier, at an average depth of 1800 feet. 



Lamouroux has estimated the marine Algse as ranging from 5000 

 to 6000, which, he has shown, are distributed in various regions. 

 Their distribution is much influenced by the degree of exposure to 

 light, as well as by the motion of the waves. Great depths of the 

 ocean are observed to exercise an influence on marine vegetation. 



