LESSONS IN BOTANY. 



177 



LESSONS IN BOTANY. XIX. 



SECTION XXXV.-LABIAT.S, OR THE LIP-FLOWER TBIBE. 



i peraon who has attentively examined the flower of a 

 mint, sage, or lavender plant, cannot fail to have remarked tho 



n.iiiirity which its mouth bean 

 to tin- open jaws of an animal; hence 

 tin' tiTiu labiate, <>i- /iy/(/, from the 



hiliium. o /<> (a more expressive 

 mil' iniL'lit bo found), which has been 



1 to them. 



- r<tcteriilic8 : Calyx free, regular 

 or irregular ; corolla hypogynous, mono- 

 petalous, bilabiate ; atameus inserted on 

 the tube of the corolla, four, didyna- 

 in. nn, or two; fruit composed of four 

 urh:>nia ; seeds dicotyledonous, exalbu- 

 miiiuus ; radicle inferior ; leaves opposite 

 or \ crtioillate. Such are the scientific 

 points which characterise the Labiates, 

 but we shall be able to recognise them 

 by superficial characteristics. 



Reversing the usual order of our in- 

 vestigation, let us first pay attention to 

 the ovary. When ripe, it displays the 

 four nut-like fruits, termed by botanists 

 achcenia, as we found in the Borage 

 tribe; and when it is considered that this 

 kind of fructification does not exist in 

 any natural order, save the Boraginacece 

 and Labiuhr, the value of this charac- 

 teristic will be evident. Further than 

 this, there is no similarity between the 

 two natural orders. The Borage tribe 

 is insipid, tho 

 Labiate tribe 

 powerfully odo- 

 rous. The Bo- 

 rage tribe has 

 gyrate inflores- 

 cence; the La- 

 biate tribe has 

 not. The Bo- 

 rage tribe has 

 round, hairy 

 stems ; the La- 

 biate tribe, 

 stems which are 

 square and an- 

 gular The 

 flowers ot the 

 borage tribe 

 have a regular 

 corolla, in those 

 of the Labiate 

 tribethe corolla 

 is irregular; 

 those of the Bo- 

 rage tribe have 

 five stamens, 

 whereas those 

 of the Labiate 

 tribe have four 

 two long and 

 two short (Fig. 

 172, a, 6). 



The princi- 

 pal habitat of 

 this natural or- 

 der is tho zone 

 bounded by the 

 fortieth and fif- 

 tieth parallels 



of northern latitude. Their number diminishes towards the tro- 

 pics and either pole. Beyond the Tropic of Capricorn they are 

 seldom found, and are altogether banished from the polar regions. 



Most of the Labiatae contain a volatile oil, a bitter gum- 

 resinous principle, and gallic acid. The purely aromatic species 



38 N E 



Characteristics : 



mint, thyme, sage, rosemary, are employed in domestic economy, 

 and as perfumes, in addition to their medicinal OMC. 



SECTION XXXVI. SCBOPHULARIACEJB, OB THE FOX- 

 GLOVE Tl 



Calyx free ; corolla hypogynoui, mono 

 pctaloun, generally irregular and bila- 

 biate ; stamens inserted on the tube of 

 the corolla, four didynamotu, or two; 

 ovary, bilocular, many-seeded ; fruit cap- 

 sular, rarely fleshy ; seeds dicotyledo- 

 nous, albuminous. 



Taking a foxglove as oar specimen, 

 the student cannot fail to be struck 

 with a general resemblance subsisting 

 between a flower of a labiate plant and 

 a flower of the foxglove, as shown in 

 Figs. 170, 171, the example of the 

 labiate plant being drawn on a larger 

 scale than the foxglove. 



In the hitter, however, the irregu- 

 larity of corolla (Fig. 99, page 280, 

 Vol. I.) is still more marked. 



The ovary, moreover, is different from 

 the former ; we no longer see four 

 lobes, but two, each of which is a cell, 

 which, if cut open, displays a great 

 number of seeds. 



The Foxglove tribe is not completely 

 banished from any region, although it 

 more especially belongs to warmer part* 

 of temperate climes. Between the 'to- 

 pics and in the polar regions they are 

 comparatively rare. The Scrophnl *ria. 

 ' from which the name of the order '8 de- 

 rived, w & BO 



109. THE IMPERIAL PAULOWNIA (PAULOWNIA IMPERIALI8). 170. THE COMMON FOXGLOVE (DIGITAL!* 

 rtTRPUREA). 171. AN EXAMPLE OF A LABIATE PLANT. 172. THE COMMON HYSSOP (HT8SOPU8 

 OPFICIKALIS. 



called oa ac- 

 count of ite 

 supposed effi- 

 cacy in the cure 

 of scrofulous 

 diseases. Un- 

 fortunately ,the 

 opinion is not 

 borne out by ex- 

 perience. The 

 foxglove (Digi- 

 talis purjmrea, 

 Fig. 170) is an 

 exceedingly 

 valuable plant, 

 owing its effi- 

 cacy to the pre- 

 sence of a che- 

 mical sab- 

 stance termed 

 digit aline. Ita 

 great use is to 

 diminish the 

 action of the 

 heart, and con- 

 sequently to 

 lessen the vio- 

 lence of the 

 blood's circula- 

 tion. Digitalis, 

 however, and 

 all its prepara- 

 tions, are so 

 powerful in 

 their action, 

 that they 

 should never 

 be adminis- 

 tered except under the sanction of a medical man. The foxwort, 

 veronica, snapdragon, monkey-flower, and verbascum, all belong 

 to the natural order we are now considering ; but perhaps the 

 most beautiful species in this family is that of which a repre- 

 sentation is shown above in Fig. 169, the Pauloicnia imperiaKt, 



