FLOWERING. 75 



opposite leaves and meet around the stem, each pair constitutes a ver- 

 ticilaster or verticil, as in catmint, hoarhound. 



363. How THESE MODES ARE MUTUALLY RELATED. All the forms of inflorescence 

 above described may, after all, be shown to be but modifications of a single type, 

 as follows : 



Let us commence with the spike, a slender racliis with sessile flowers. Conceive 

 that pedicels be developed for the flowers, = a raceme ; let the pedicels branch, = 



22S 227 



Diagrams illustrating the forms of inflorescence ; graduated from tlic spike 

 umbel, showing how related to each other. 



> the compound 



a panicle ; or let them all be lengthened to the height of the rachis, = a corymb. 

 Now suppress the rachis to a pMnt, making all the pedicels equal, =- an umbel. 

 Once more, suppress all the pedicels, = a head. Now, if in each case we suppose 

 the evolutions of the flowers to bo reversed, wo have a cymose inflorescence. Fi- 

 nally, by a metamorphosis still more remarkable, 



The entire inflorescence is sometimes transformed into attenuated 

 tendrils, as in the grape. 



FLOWERING. 



364. DEFINITION. In the bud the floral leaves (sepals and petals) 

 infold the floral organs (stamens and pistils) and conceal them from 

 view. Flowering consists of the opening or expansion of these envel- 

 ops, displaying every organ now perfected in growth and beauty, and 

 ready for the exercise of its function. 



365. PERIOD OF FLOWERING. Each species of plant has its own 

 special season for flowering, uniform in the same climate, but varying 

 in different climates according to the general temperature. Hence each 

 month and each day of the month mark the date of flowering for some 

 one or more species, and these facts, when duly observed and recorded 

 in then- proper order, constitute the floral calender for that locality. 



366. THE FLORAL CALENDAR is an index of climate, and may vary 

 to a considerable degree in different years for the same locality or for 

 different localities in the same yeair. Such a calendar is prepared by 

 the botanical student when he carefully journalizes his discoveries from 

 day to day throughout the season. 



