74 GENERAL BOTANY 



often a very useful article of food, as the COLOCASIA 

 and ONION. 



In colder countries where there is much more differ- 

 ence between the seasons, and where during one part 

 of the year active life ceases, not because of dryness 

 but because of the cold which prevents roots taking 

 up water, there are plants which live only two years,, 

 and spend the first season in purely vegetative work, 

 making large quantities of food and storing it for use 

 during the second season, which is devoted to the pro- 

 duction of flower-seeds, that is, to reproductive work. 



These are termed biennials, and most of them 

 have rather thick underground parts in which food- 

 material made during the first season is stored for 

 making the seeds the second year. For this reason 

 many of them, like the sixth group of perennials,, 

 are valuable food plants, and some, as the Carrot, 

 Radish, Turnip, are grown in this country. 



Then again there are those referred to in the last 

 chapter (section 12) which live for many years, but 

 flower only once and die soon after the seeds have 

 fallen. These may be called multiennials. They have 

 mostly stems of a palm nature, as the Talipot-palm 

 (CORYPHA), or the so-called Aloe (AGAVE). 



Looking at plants from the point of view of the 

 length of their lives, we class them as annuals, biennials,, 

 multiennials and perennials ; looking at them from 

 the point of view of their nature and substance, we 

 may classify them as : 



(l) herbaceous, when they are soft and not woody, 

 for example, the ordinary field and garden 

 annuals and some perennials. 



