Classification of Plants 



199 



In the German system of Engler, flowers with inconspicuous 

 or no perianth occupy the lowest rank.^ These together with 

 flowers with separate petals are united under Archichlamydece. 

 In both systems there is a tendency, as development proceeds, 

 for the axis to become shortened and finally concave. Parts 

 become definite or reduced in number and arranged in cycles 

 (whorls). After the perianth has become cyclic, sporophylls 

 may still occur spirally. Such flowers are known as spirocyclic. 



Fig. 193. — Spirocyclic flower of Magnolia. The perianth is in whorls, the 

 stamens and ovaries in spirals. 



With these changes coming into vogue, another tendency 

 appears. Parts of a cycle "fuse" with one another. The 

 term leads one to suppose that parts which were at first separate, 

 join. As a matter of fact, after the rudiments of a cycle are 

 laid down, the floral axis beneath develops in a ring or zone 

 instead of in separate portions (zonal development). The 



1 In this system incomplete flowers do not form a distinct group as in 

 the former but are regarded, in many instances, rather as a primitive con- 

 dition than as incomplete by reduction. 



