CHAPTER XI 



DIVISION OF TERRESTRIAL PLANTS ACCORDING TO 

 THEIR LONGEVITY AND FREQUENCY OF SEEDING 



Division of Plants according to tlieir Longevity. 



1. Annuals. — These plants live through one or part of 

 one vegetative season and then perish, after providing for 

 the continuance of the race by the production of seed — 

 e.g., poppies, groundsel, chickweed. There are two kinds 

 of annuals : 



(a) Those which germinate from seed in the spring, and 

 perish towards the close of the vegetative season — summer- 

 annuals — e.g., poppy. 



(6) Those which germinate from seed in the autumn, 

 forming small plants with a few leaves, arranged on the 

 rosette plan, close to the ground, and continue their 

 growth in the following spring — autumn- annuals. They 

 flower early, and perish before the hottest part of the 

 summer sets in. Annuals belongiag to this class must 

 seed very freely because the fatality among the seedlings 

 during the winter is very great. 



In both cases there is a season during which the plants 

 are not seen at all. In the case of summer-annuals this 

 season is the period of vegetative rest, winter ; in the case 

 of autumn- annuals, which are vernal bloomers, it is the 

 summer, when hot, dry conditions bring about a period 

 physiologically unfavourable to the plants. The latter 

 are found chiefly in dry steppe-regions, or in sandy and 

 stony places which become very hot and dry in summer. 

 They are not common in England, but a few are found 

 on sand-dunes, a habitat specially remarked for summer 

 drought — e.g., the vernal whitlow-grass (Draba verna), 

 the early forget-me-not {Myosotis collina), and the small 

 mouse-ear chickweed (Cerastium semidecandrum), 



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