302 GROWTH 



381. Length of Life of an Annual. Ascertain the time neces- 

 sary for some rapidly developing annual to attain full stature, 

 form and cast off its seeds, and die. 



382. Period Necessary for Maturity of the Cells of a Stem. Cut 

 down a tree at least 40 cm. in diameter and test the medullary 

 rays to ascertain to what age these elements survive. Also test 

 the tracheids and find if they live beyond the season in which 

 they are formed. 



383. Senescence and Death in an Annual Plant. Examine any 

 convenient herbaceous annual, and note the first stages in the 

 steps leading to its death. In what organs are the phenomena 

 first visible ? Cut sections of the dying stems and leaves and note 

 changes in color of the walls and constitution of the living matter. 

 Note the relation of the death of the plant, and the maturity 

 and dissemination of the seeds. What organs survive longest? 



384. Death of a Perennial. Select a tree of any convenient 

 species in a forest and ascertain the conditions which have caused 

 its death. Note the presence or absence of parasitic fungi, and 

 determine whether these have gained a foothold in decaying 

 tissues, or 'have attacked sound wood or living tissues. Examine 

 the tree for damage caused by animals. What portion of the 

 tree perished first ? 



385. Correlations in Growth. A multicellular plant body with 

 differentiated tissues presents a diversity of complementary func- 

 tions, which are involved in a series of mutual interactions of the 

 most complex character. The modification of any function, or 

 changes in the organ, in which the function is carried on, produces 

 a disturbance in all of the other organs of the plant constituting 

 an effort toward readjustment to the altered conditions. All of 

 the activities of the organism are correlated, but it will be most 

 convenient to study the results of this feature in the organization 

 of the plant in growth. The development of a fruit as a result of 

 the pollination of the pistil, the development of a lateral branch 

 to take the place of a main stem which has been removed (130).. 

 and the formation of the missing organs from a stem, root, or leaf 



