344 



THE POPULAE EDUCATOR 



LESSONS IN BOTANY. XXIV. 



SECTION XLV. CONVOLVULACE.E. 



Characteristics : Calyx free, corolla hypogynous, monopetalous, 

 regular ; aestivation contorted j stamens inserted into the tube 

 of the corolla, their number equal to that of the lobes ; ovary 

 two to four celled ; ovules solitary or twin, erect ; fruit capsular 

 or bacciform ; seed dicotyledonous, curved, im- 

 bedded in mucilaginous albumen ; radicle in- 

 ferior. 



The Convolvulacece derive their name from 

 the property which most, although not all of 

 ithem, have of climbing up other plants. They 

 abound in the torrid zone, in low marshy situa- 

 tions, especially near the sea. In proportion 

 as the distance from the equator diminishes, 

 so do the Convolvulacece become more rare. 

 In temperate climates only few species exist ; 



186 



185. PURPLE IPOMS:A (IPOM*;A TYRIANTHINA) . 186. 

 THREE-COLOURED CONVOLVULUS (CONVOLVULUS 

 TRICOLOR. 187. DODDER (CUSCUTA). 



and in the frigid zone they are altogether ab- 

 sent. The predominant medical quality of the 

 Convolvulacece is that of purgative. Jalap 

 and scammony are both derived from this na- 

 tural order. Even the roots and tubers of our 

 own native species are purgative, though, in 

 consequence of the low price of jalap, they are 

 at present never employed for this purpose. 



It is scarcely necessary to append an engraving for the pur- 

 pose of giving the reader a general idea of the external character- 

 istics presented by this natural order. Nevertheless, we do this 

 that we may introduce three beautiful species, the Ipomcea tyrian- 

 thina (Pig. 185), or purple ipomsea, a stove evergreen climber, 

 indigenous to Mexico, the Convolvulus tricolor (Fig. 186) ; and 

 the Cuscuta, or dodder (Fig. 187). It should be said that 

 although the dodders are generally referred to the order Convol- 

 vulacece, by some botanists they are grouped into a small distinct 

 order termed Cuscutaceos. Like the Convolvulacece they are 

 climbing plants, but they differ from them in being leafless and 

 parasitic, often causing great injury to crops of leguminous plants 

 and flax, to the stalks of which the stem of the dodder attaches 

 itself by small rootlets, the original root which had been sent 



out from the seed when it germinated in the ground dying away 

 as soon as the stem has commenced to throw out rootlets. 



SECTION XLVI. POLEMONIACE-a:, OK PHLOXWOKTS. 



Characteristics : Corolla hypogynous, monopetalous, regular ; 

 stamens inserted upon the tube of the corolla, in number equal 

 to its lobes, and alternate with them ; ovary three to five celled ; 

 placentae parietal ; fruit capsular ; seeds erect 

 or ascending dicotyledonous ; straight in a 

 fleshy albumen. 



The student cannot look at a member of 

 this natural family without being cognisant of 

 a general similarity between this natural order 

 and Convolvulacece. Not only is the general 

 aspect of the flower similar, but there is also 

 a certain similarity of anatomical structure. 

 In both the flower is quinquepartite ; but the 

 Polemoniacece differ in several points from 



188. WHITE PHLOXWORT (POLEMONIUM ALBUM). 189. 

 VIRGINIAN HYDROPHYL (HYDROPHYLLUM VIR- 



GINICUM). a, COROLLA OF VIRGINIAN HYDROPHYU 



the Convolvulacece, as will be seen from an 

 inspection of Fig. 188, which is a representa- 

 tion of the leaf, bud, and blossom of the 

 Polemonium album. 



SECTION XLVIL HYDBOPHYLLACE-E. 

 Characteristics : Calyx free ; corolla hypo- 

 gynous, monopetalous, regular ; stamens in- 

 serted upon the tube of the corolla, in number equal to the divi- 

 sions of the latter, and alternate with them ; ovary unilocular 

 or imperfectly bilocular ; placentae parietal ; ovules solitary or 

 numerous on each side of the placentas ; fruit capsular or almost 

 fleshy ; seeds few in number ; seed dicotyledonous ; embryo 

 straight, imbedded in an abundant cartilaginous albumen. 



Members of this natural family, to which the genus Hydro- 

 phyllum lends its appellation, are herbs either annual or peren- 

 nial, possessing an aqueous juice ; an angular stem considerably 

 ramified ; leaves alternate, especially towards the upper part ot 

 the vegetable, usually deprived of stipules ; flowers complete, 

 regular, disposed in corymbs or unilateral spikes, scorpioidal, or 

 scorpion-like, simple, or dichotomous, rarely solitary; calyx 

 deeply fissured in five divisions, imbricated in aestivation, and 



