SEED-BEARING PLANTS 39 1 
having prominent midribs and pinnately divided (Fig. 
285). The leaves endure for a year or more (varying 
with the species), and are then replaced by a fresh crown. 
The duration of each crop of leaves is said to vary accord- 
ing as the plant grows wild, or in botanic gardens and 
FIG. 286. Cycas revolula. Terminal bud of foliage leaves just opening. 
Nearer view of Fig. 285. Note the circinate vernation of the leaf-pinnules, 
but not of the entire leaf. 
conservatories. Thus, when temperature and rainfall are 
excessive, Cycas circinalis may produce two crowns of 
leaves a year, instead of the one crown commonly produced 
in green houses. 
The young leaves are curled up at the tips, unrolling 
as they grow. In the genus Cycas only the leaflets are 
