MORPHOLOGY <>F TIIK l;o<>r. 



">l. But some plants, such as the Radish, which when they 

 spring from seed in autuinii arc true liieiinials, will \vhcn raised 

 in spring pass on directly to tlic (lowering stage in summer, or 

 \vlicn sown after the warm season begins will often run through 

 their eour>e as annuals. Then there are various liieiinials which 

 thicken the root verv little and hold their leaves through the 



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winter. Between these and winter annuals no clear demarcation 

 can be drawn. As respects annual and biennial duration, the 

 terms may for the most part be applied indiscriminately to the 

 plant or to the root. We may say either that the plant is a 

 biennial, or that its root is biennial. 



")."). Perennials are plants which live and blossom or fructify 

 year after year. They may or they may not have perennial 



roots. In trees and shrubs, also in 

 herbs with growth from year to year 

 from a strong tap-root, the root 

 is naturally perennial. But in most 

 perennials with only iibrous roots, 

 these are produced anew from time 

 to time or from year to }'ear. Also, 

 \\hile some such roots remain fibrous 

 and serve only for absorption, others 

 may thicken in the manner of the 

 ordinary biennial root and serve a 

 similar use, /. e. become reservoirs of 

 elaborated nourishment. The Dahlia 

 (Fig. (IS) mid the Peony afford good 

 examples of this. Sweet potato is 

 another instance. 1 Most such roots 

 have only a biennial duration : the}- 

 are produced in one growing season: they yield their store to 

 form or aid the growth of the next. When perennials store up 

 nutritive matter underground, the deposit is more commonly 

 made in a subterranean portion of the stem, in tubers, conns, 

 bulbs. &<. (See 11 :-! _>:>.) 



."><;. The distinction between annuals and biennials is at times 



so dillieult. and the particular in which they agree SO manifest. 



-namely, that of blossoming only once, then dying, as it were 



by exhaustion. that it was proposed by I )e( 'andolle to unite 



1 II is only by the readiness of this root to produee adventitious buds, 

 especially from its upper part, that it lias been mistaken for a tuber, sueli 

 as the eonnnon potato. 



Fit;. i;s. Kasrided and tuln-nnis i>r fusiform (secondary) roots of Dahlia: a, a. buds 



on liasr "I' thi' strm 



