LESSONS IN BOTANY. 



to a correct appreciation of the functions which those part* of SECTION XTVI.-MYRTACEJE, OR THE JffTBTLB TBIBK. 

 vegetables exposed to the air and HUH, especially leaves, are Characteristic* : Calyx, adherent ; petals, in number equal to 

 destined to perform, and points oat the necessity of giving the divisions of the calyx, inserted on a disc around the throat 

 vegetables abundant air and light, if we would have thorn bring ' of the latter ; aestivation imbricated, rarely absent ; stamens, 

 forth their natural productions. To stimulate those natural ordinarily indefinite; ovary, usually two to six-celled, plnriovnlar, 

 productions i-. in most cases, the main object of agriculture or containing many ovules; ovules, pendulous, reflexed or 

 and horticulture ; occasionally, however, as in the example of I curved ; style, simple ; fruit, dry, or a berry ; seed, dicotyledo* 

 celery, the ob- 

 ject kept in view 

 is the reverse of 

 this. 



The odoroua 

 principle in cer- 

 t-iin Umbelliferw 

 is of a resinous 

 character; thus 

 assafcetida is the 

 produce of 



ii'-'i . 



Such is the 

 long list of gene- 

 ral characters by 

 which botanists 

 recognise a plant 

 of this great 

 natural order; 

 nevertheless, 

 myrtles, like 

 many other 

 members of the 

 vegetable world, 

 have a sort of 

 physiognomy of 

 their own, more 

 easily recognised 

 than described. 

 Perhaps the 

 fragrant odour 

 diffused by these 

 beautiful plants 

 is one of their 

 most prominent 

 characteristics. 

 All the sub- 

 stance of a 

 myrtle is more 

 or less saturated 

 with this odor- 

 ous matter. Now 

 we find it as- 

 sumes its great 

 est power in the 

 bark, now in 

 the flower buds, 

 now in the 

 leaves; but it is 

 everywhere pre- 

 sent more or less- 

 Supposing the 

 reader to have 

 before him a leaf 

 of the common 

 myrtle, he need 

 not be told that 

 the leaf is odo- 

 rous, especially 

 when crushed 

 between the 

 fingers. Now, 

 in what does the 

 odour consist, 

 and where does 

 it come from ? 

 139. DIDISCTS CCRTN This, like the 



LEUS. 140. FLOWER OF DIDISCUS CJKRULEUS, ENLARGED. 141. SECTION OF BLOSSOM IND OVARY OF greater number 



MYRTLE. 142. TRANSVERSE SECTION OF OVARY OF MYRTLE. 143. THB COMMON MYRTLE (MYRTC8 o f odorOUS prin- 



COMMUNIS). 144. BLOSSOM AND LEAF OF THE CLOVE-TREE (CARYOPHYLLUS AROMATICU9). 145. FRUIT OF cjples furnished 

 THE CLOVE-TREK. 



an 



umbelliferous 

 plant growing in 

 Persia. Opopo- 

 nox and ammo- 

 niacum, both so 

 valuable in me- 

 dicine, arc also 

 the produce of 

 umbelliferous 

 plants. 



Many of the 

 Umbelltferce con- 

 tain sugar, BO 

 like that of the 

 cane in every 

 respect that 

 sugar- loaves 

 may be mode of 

 it Thus the pre- 

 sence of sugar 

 may be recog- 

 nised by the 

 taste in the root 

 of the carrot and 

 the parsnip; 

 also, in the root 

 of celery, al- 

 though less evi- 

 dently. Indeed, 

 sugar may be 

 regarded as a 

 pretty general 

 concomitant of 

 the umbellifer- 

 ous structure ; 

 even in the juice 

 of the poisonous 

 hemlock it may 

 be discovered by 

 chemical tests. 



It would bo a 

 needless task to 

 occupy space in 

 pointing out the 

 various uses of 

 umbelliferous 

 plants to man. 

 The so-called 

 carraway, cori- 

 ander, and anise- 

 seeds, flavour 



our pastry and confectionery ; carrots and parsnips are amongst 

 the most favoured articles of our food ; even the noxious hem- 

 lock yields a valuable medicinal substance, conia; and the resin- 

 yielding umbel-bearers pour forth their treasures in great 

 profusion. By far the greater number of this family have white 

 flowers ; some, like the fennel, have yellow flowers, and a few 

 have blue ones. Of the latter kind are most of the Eryngo 

 genus, and the beautiful Didiscus Cceruleus, of which we now 

 give a representation (Fig. 139). 



141 



137. BLOSSOM OF PABSLET, XNLAKGED. 138. FOOL'S PARSLEY (JETHCSA CYNAPItTM). 



to us by the 

 vegetable king- 



dom, is a volatile oil, and in the myrtle leaf it is secreted 

 by specific organs, denominated glands. If a myrtle leaf be 

 held between a candle, or other source of light, and the eye, 

 these little glandular bodies will be seen like so many specks } 

 it is within these glands that the volatile oil remains encased. 

 Glands are not necessary for the secretion of volatile oil, nor are 

 they necessarily confined to leaves. They exist in large quan- 

 tities in the skin of members of the orange tribe, and it is from 

 them that the inflammable volatile oil is esoitted when a piece 



