leaves are formed, the intervening parts grow very lit- 

 tle, and so do not separate the successive leaves or cir- 

 cles of leaves. The torus is more or less broadened or 

 elongated to permit the suitable growth of the crowded 



leaves. In the strawberry it is high, dome-shaped 

 (Figs. 826, 827); in the raspberry the torus remains 

 (S, Fig. 828) when the little drupes are removed; in the 

 rose it is urn-shaped, bearing the leaves on the edge and 

 inner face ; in the mouse-tail it is much elongated. 

 When a number of tlowers are crowded together their 

 leaves are developed from a common torus, as in sun- 

 flower and chrysanthemum and other members of the 

 CompositiB (Fig. 829). The common torus may be 

 broad and flat, with the flowers scattered over it, as in 

 Dorstenia (Fig. 732) ; or even hollow, as in the fig (Fig. 

 821), with the minute flowers on the nearly enclosed 

 inner face 



Floial Uaies —The leaves of the flower form two 

 serift; tht outer protective and attractive leaves, the 

 fl , ' I I 1 i tti nmi I ':piynn,i, illeaves. Thefloral 



1 ' 1 tni_ui ti il I into an outer set, the 



' ' i T 111 ; // / The calyx leaves, 



^^ll I ill .1 j :l 111.1 the corolla leaves 



I'lI I il 1 iL iiL imiL ui li s', different from the 



petiK iiisizi , sli ipeind color Thcj are oftenest green, 

 anil usuallj smaller and simpler than the petals. In the 

 bud they usually completely cover the inner leaves. 

 The sejuK ind petils oftentimes do not remain distinct 

 thioiuli u^ til li development, but each set grows as a 

 siii^l I I 1 t 1 t which has been made the basis of 



<- 1 1 111 iti n t ihi ingiosperms Corollas of a single 

 pii I I 111 suit. I ,,amopetalous (Fig 830). The sepals 

 ire iiinie tumiiinnh inseparate thin the petals. 



The ippaieut union of the flortl leaves comes about 

 generalh m this -nav On the -voung torus the rudi- 

 ments ot the sepals and petals irise as rounded knobs, 

 which for a longer or shorter tune grow independently 



If they develop independently until their growth ceases, 

 the sepals or petals are distinct, each one being sepa- 

 rately attached to the torus. On the other hand, after the 

 leaf rudiments have grown independently for a time, a 

 zone of the torus, both under and between two or more 

 adjacent rudiments, may begin to grow, lifting them on 



FLOWER 593 



its margin. In that case, when fully grown the calyx or 

 corolla appears as a single piece, whose free edge is 

 more or less deeply lobed, according to the relative dura- 

 tion of independent development of the rudiments. 



The calj-x and corolla are sometimes united. This 

 comes about in a similar way. Each begins to develop 

 independently ; later the tissue between calyx and co- 

 rolla shares in the growth and both are raised' on a com- 



The form of the mature floral leaves depends largely 

 on the relations of the flowei to insects \^hil h i i it the 

 flowers for nectar or pollen The floral lea\ i iie often 

 irreguHr ind unequal so as to foim suit ibli 1 aiding 

 places nectir f,lauds j,uides to tli m t u t — dl de- 

 vices to facilitate the jin pel ti ui I i I | 11 ii b\ the 

 visitors e g the sweet pea an I ili i ) i| ih n i. eous 

 flowers most orchids etc (see 7 // i il n) 



The color of the corolla and ad] aint p iits i due to 

 the presence m the cells of colored sap oi speci il tolor- 

 bodies In the latter case the pigment is sometimes 

 crystalline It is not possible to determine without mi- 

 croscopic examination m which way the color is pro- 



QQ 



duced. Most blues are due to colored sap; many yel- 

 lows and reds to color-bodies. 



The velvety appearance of many petals is produced by 

 the outgrowth of the surface cells into conical or dome- 

 shaped protuberances. 



The odor of flowers is usually due to the presence of 

 volatile oils in the surface cells of the petals or sepals, 

 or both. These oils are present in small amount only. 

 They are sometimes found only on the outer face, or 

 only on the inner face, or they may even be restricted 

 to certain lines or patches. 



Tlie stamens. — The stamens commonly consist of two 

 parts, a stalk the filKment bearing a larger poi tic n the 

 anther (Pig. 831 1 The fll iment is usu 

 ally rigid enough to sustain the weight 

 of the anther but at maturity it is 

 sometimes so long and slender that the 

 anthers hang as by a thread (so m 

 grasses). The fiUnient is sometimes 

 so short as to seem wantin,^ the antlu r 

 is then said to be sessik The hla 

 ments are often united with one 

 another or with the corolla by the 

 mode of growth already described In 

 the latter case the stamens seem to 

 arise from the corolla Only rarely 

 are the stamens and carpels united 



The anther is the part of the stamen 

 which bears the spore-cases or pollen 

 sacs (sporangia). (The sporangia are 

 not always borne on stamens. In a few 

 plants they are sunk in the stem of the 

 flower.) Of these there are commonly flower of Wi now. 

 four, more rarely two or one. When Showing two sta- 

 the anther was looked upon as a cham- mens; their an- 

 bered body, the sporangia were called ^''^ ^^^ "* "■ 

 thecie, or cells. Thus in descriptive botany the anther 

 is said to be "2-celled" or "4-celled." The sporangia are 

 partly free and partly imbedded in a mass of tissue 



