16 THE STErGGLE FOE EXISTENCE. 



wise more tenacious of Kfe than others, the various cUmatic factors 

 ■will afPect different plants differently. Nevertheless the victory 

 will not always be for the stronger plant, for the weaker and lower 

 plant may be sheltered by its more vigorous and taller neighbour, 

 which, as often as not, may be so injured, especially during a sea- 

 son of exceptional frost or in an exceptionally heavy hailstorm, as 

 to allow the former to get ahead of it. Hail, according to the size 

 of the stones and the force with which these fall, may (i) destroy 

 flowers and fruit, while at the same time injuring to a greater or 

 less extent the foHage, or (ii) destroy the entire foliage as well, or 

 (iii) also break off twigs and even the smaller branches, or (iv) in 

 addition to (iii) bruise and even gash the baris of the trees. The 

 wind might uproot or break off an important Umb of the strong 

 tree, under the weight of superincumbent snow one or more large 

 boughs might snap off, lightning might select the tallest or largest 

 tree, and so on ; thus allowing the weaker to conquer in the strug- 

 gle for existence. 



(d) Conflagrations. — Fire may kill a plant-part either (i) by 

 charring its vital portions, or (ii) by suddenly converting the mois- 

 ture contained in it into steam and thus causing rupture of the 

 tissues and disorganisation of the protoplasm and ceU-sap, or (iii) 

 by mere over-transpiration and formation of substances other than 

 what would result if the life-functions of the part were not disturb- 

 ed. The resistance offered to damage caused by fire will depend 

 on the size and vigour and Kgnification of the plants, the number 

 of dormant buds they possess, the size and height of their crown 

 and the not too forward condition of the current year's buds when 

 the fire occurs. But, as often happens, trees more favoured than 

 others in the above respect may, from being situated near a mass 

 of inflammable material or from any other accidental cause, be so 

 injured as to throw them hopelessly back in the race of life. In the 

 case of conifers, which species produce very few or no dormant buds, 

 and of broad-leaved species which coppice badly, the smaller plants 

 will stand comparatively little chance of recovery. In the case of 

 evergreen species, all other tilings being equal, the importance of 

 forest conflagrations as an effective factor in the struggle for existence 

 will be very considerably diminished, \\hile, in that of deciduous 

 kinds, it will be shghter, the more nearly they approach the character 

 of an evergreen. 



(e) Floods.— FlooA?, may injure plants in nine different ways: 



(i) by bending or breaking them, (ii) by straining or breaking 



