970 



A TEXTBOOK OF THEORETICAL BOTANY 



Fig. 959. — Coleus blumei. Plant showing leaves 

 with edges vertical, in strong sunlight. 



Fig. 960. — Brassica oleracea \ar. gennuifera. (Brussels 

 Sprout.) Longitudinal section through a bud to 

 show the packing of the young leaves. 



expect to arise from the independent growth of each lamina within the limits 

 of the bud, hut is evidently the result of co-ordinated growth, the manner 

 of which is not yet understood. The particular type of folding is remarkably 

 constant in each species and is known as the ptyxis. The variety of such 

 arrangements is very great. In Monocotyledons the conditions are usually 

 relatively simple, the leaves being either tightly rolled together into a single 



