46 SCIENCE PRIMERS. [XL 



flower furthest from the axis opening first, and that 

 terminating the axis last of all. Such are centripetal 

 inflorescences, also called indefinite, because the axis 

 goes on elongating after the first flower opens. When 

 the flowers are crowded this difference of order of 

 opening is quite as conspicuous. Thus the elder in- 

 florescence is centrifugal, the daisy and carrot centri- 

 petal. The teazle is a very rare exception ; in it the 

 middle flowers, those half-way up the head, open first, 

 and the order of opening is both upwards and down- 

 wards from these : this is called a mixed inflorescence. 



78. The common sorts of inflorescence are 



(a) The spike, where the flowers are sessile on the 

 peduncle (plantain). A catkin is a spike that falls 

 away after flowering (walnut, oak, poplar, birch). 



(b) The raceme is a spike with pedicelled flowers 

 (currant, foxglove, snapdragon, mignonette). 



(c) In the head, the flowers are sessile and crowded 

 in a dense mass (daisy, teazle, scabious, clover). 



(d) The panicle is a raceme in which each pedicel 

 branches again (oat, horse-chesnut, lilac). 



(e) In an umbel all the pedicels start from one 

 point and the flowers reach about the same level; 

 (flowering rush, onion, cowslip) ; when the pedicels 

 of the umbel are again umbelled the umbel is called 

 compound (carrot, parsnip). 



(/) In the corymb, the flowers reach the same 

 height, but their pedicels do not spring from the same 

 level; (elder, star of Bethlehem, hawthorn.) 



79. The leaves of the inflorescence are modifica- 

 tions of the same organs as occur on the stem, but they 

 serve a different purpose, being usually protecting 

 organs to the young flower ; those at the base of or 



