400 



RELA TION TO ENVIRONMENT. 



leaf just below. In some stems, according to the leaf arrange- 

 ment (or phvllotaxy), one would pass several times around in 

 ascending the stem before a leaf would be found directly above 

 another, which would be such a distance below that it would not 

 be shaded to an appreciable extent. Interesting observations 

 can be made on different plants to work out the relation of dis- 

 tance of leaves on the stem to length of the upper and lower 



Fit'. 441'- 

 Palm .shriwiny radiate arrangement rif leaves and the petiole of the leaf func- 

 tions as stem in lifting leaf to the light. 



leaves; the number of vertical rows on the stem compared to 

 the width of the leaves; and tlie relation of these facts to the 

 problem of light sup])l\-. Related to the sjdral pattern is that of 

 erect stems with opposite lea\es. Here each pair is set at right 

 angles to the direction of the pair abo\-e or below. 



781. Radiate pattern. — This pattern is present in man\- grasses 

 and related plants with narrow lea\cs and short stems. The 

 leaves arc often \-ery crdwdcd al llic base, luit li\- radiating in 

 all directions irom the linrizunlid to Ihc M'ilii.al, aliundant ex- 



