LABORATORY STUDIES OF THE STEM 45 



under autiiinii or winter rains, grow more or less during winter, blos- 

 som, fructify, and perish in the following spring or summer. Annuals 

 are fibrous rooted. 



67. Biennials, of which the Turnip, Beet, and Carrot are familiar 

 examples, grow the first season without blossoming, usually thicken 

 their roots, laying up in them a stock of nourishment, are quiescent 

 during the winter, but shoot vigorously, blossom, and seed the next 

 spring or summer, mainly at the expense of the food stored up, and 

 then die completely. 



68. Perennials live and blossom year after year. A perennial 

 herb, in a temperate or cooler climate, usually dies down to the 

 ground at the end of the season's growth. But subterranean portions 

 of stem, charged with buds, survive to renew^ the development. 

 Shrubs and trees are of course perennial; even the stems and branches 

 above ground live on and grow year after year. 



VII. LABORATORY STUDIES OF THE STEM 



At the beginning of the study of the stem, it is well to 

 recall the fact that a flowering plant typically consists of 

 root, stem, and leaf. Stems and leaves may be so dis- 

 guised as not to be readily recognized in their true charac- 

 ter. Thus some stems are so modified as viery closely to 

 resemble leaves, while others assume the general appear- 

 ance of roots. Yet there are, with few exceptions, certain 

 marks of the stem proper even in these dissembled forms. 



The Marks of the True Stem 



1st. The stem is characterized by a general plan of 

 construction, as viewed externally, differing essentially 

 from that of either root or leaf. 



What is the Plan ? 



2d. It bears appendages at certain definite places. 



What are the Appendages? 



Where inserted upon the stem ? 



3d. If the stem in question is an offshoot from an 

 older one, its point of origin has a certain definite loca- 

 tion. Position determines the fact that a lateral member 

 is a hranch stem, and not a leaf. 



