40 LIFE-HISTORY 



distinguished by the name of ephemerals — e.g. Chickweed and 

 Shepherd's Purse. Annuals proper can produce only one 

 generation in a single vegetative season, because their 

 life extends over several months. A plant which germinates 

 and vegetates in its first active season, and blossoms and dies 

 in its second year, is described as a biennial — e.g. Turnip. 

 Finally, a plant which is capable of existing for several years is 

 termed a perennial; and if it can blossom only once it is 

 described as a monocarpic perennial — e.g. some Palms. 



Polycarpic plants are all perennials. They vegetate and 

 produce flowers and seeds season after season — e.g. Dandelion, 

 British trees and shrubs. 



It is more important to lay stress upon the number of times 

 a plant can flower than to consider whether the plant be annual, 

 biennial, or perennial; for the distinctions amongst these 

 latter are largely arbitrary. For instance, many plants which 

 are described as annuals can germinate in autumn, rest during 

 the winter, and flower in the following spring — in fact, they act 

 as biennials. Again, if by artificial or natural means the forma- 

 tion of fruits or flowers on an annual be prevented, the annual 

 may live for years — in fact, it becomes a perennial : e.g. 

 Mignonette artd Annual Meadow-Grass. The Daisy, which is 

 perennial in England, is annual at St Petersburg. 



METHODS OF RESTING. 



Ephemerals and annuals rest during the winter in the form 

 of seeds. In most cases their vegetative organs are dead. But 

 some annuals, when sown in autumn, can pass the winter in 

 the form of young green plants. 



Biennials and perennials retain only certain portions of their 

 vegetative organs at the resting season. There are certain 

 broad distinctions between the modes of resting of herbs and 

 of woody plants belonging to these classes. 



Resting condition of perennial herbs. — A number of peren- 

 nial herbs retain their sub-aerial stems and green leaves during 

 the winter ; amongst these are many Grasses, and Wallflowers 

 in gardens. But in the majority of perennial herbs the parts of 

 the shoot which are above the soil die down, and only sub- 

 terranean portions of the plant continue to exist at the resting 

 season. Herbaceous perennials may rest in the form of sub- 



