LABORATORY PRACTICE 



CHAPTER XI 



STORAGE 



MANY plants arise from the seed, develop stem, leaves, 

 flowers, and seeds, and die within the same twelve months in 

 which they began their life. Such are the common plants 

 which we call annuals. Other plants live on from year to 

 year and produce successive crops of flowers and seeds. 

 Such are the plants called biennials and perennials. Plants 

 living merely for a single year provide only for their off- 

 spring in maturing suitable seeds, but plants which live for 

 more than one year store away reserve materials which are 

 used for the growth of the succeeding year or years. In 

 this way plants living on indefinitely are using this year the 

 materials which they stored up last year, and are storing up 

 materials for use next year. 



The parts of the plant in which the materials are stored 

 are usually very noticeably thickened. If we examine thin 

 sections of these parts under the lenses of a compound 

 microscope and apply the proper tests, we shall find that 

 these storehouses of the plant contain starch, sugar, oils, 

 and various albuminous substances. 



I. Take a Cactus and examine, noticing : 



1. The much thickened stem and 



2. The leaves, reduced to small spines. 



3. Make a sketch of the plant showing these features. 



