SECTION 8.] ORGANS OF THE FLOWER. 79 



226. These distinctions between determinate and indeterminate inflores- 

 cence, between corymbs and cymes, and between the true and the false 

 raceme and spike, were not recognized by botanists much more than half 

 a century ago, and even now are not always attended to in descriptions. 

 It is still usual and convenient to describe rounded or flat-topped and open 

 ramification as corymbose, even when essentially cymose; also to call the 

 reversed or false racemes or spikes by these (strictly incorrect) names. 



227. Mixed Inflorescence is that in which the two plans are mixed or 

 combined in compound clusters. A mixed panicle is one in which, while 

 the primary ramification is of the indeterminate order, the secondary or 

 ultimate is wholly or partly of the determinate order. A contracted or 

 elongated inflorescence of this sort is called a Thyrsus. Lilac aud Horse- 

 chestnut afford common examples of mixed inflorescence of this sort. When 

 loose and open such flower-clusters are called by the general name of 

 Panicles. The heads of Composite are centripetal; but the branches or 

 peduncles which bear the heads are usually of centrifugal order. 



2. PARTS OR ORGANS OF THE FLOWER. 



228. These were simply indicated in Section II. 16. Some parts are 

 necessary to seed-bearing ; these are Essential Organs, namely, the Stamens 

 and Pistils. Others serve for protection or for attraction, often for both. 

 Such are the leaves of the Flower, or the Floral Envelopes. 



229. The Floral Envelopes, taken together, are sometimes called the 

 Perianth, also Perigone, in Latin form Perigonium. In a flower which 

 possesses its full number of organs, the floral envelopes are of two kinds, 

 namely, an outer circle, the Calyx, and an inner, the Corolla. 



230. The Calyx is commonly a circle of green or greenish leaves, but 

 not always. It may be the most brightly colored part of the blossom. 

 Each calyx-leaf or piece is called a Sepal. 



231. The Corolla is the inner circle of floral envelopes or flower-leaves, 

 usually of delicate texture aud colored, that is, of some other color than 

 green. Each corolla-leaf is called a Petal. 



232. There are flowers in abundance whbh consist wholly of floral envel- 

 opes. Such are the so-called full double flowers, of which the choicer roses 

 and camellias of the cultivator are familiar examples. In them, under the 

 gardener's care and selection, petals have taken the place of both stamens 

 and pistils. These are monstrous or unnatural flowers, incapable of pro- 

 ducing seed, and subservient only to human gratification. Their common 

 name of double flowers is not a sensible one : except that it is fixed by 

 custom, it were better to translate their Latin name, flores pleni, and call 

 them full flowers, meaning full of leaves. 



233. Moreover, certain plants regularly produce neutral flowers, consist- 

 ing of floral envelopes only. In Fig. 214, some are seen around the margin 



