COEOLLIFLOBxE. 311 



of Hemidesmus indicus are used as a substitute for Sarsaparilla. The 

 milky juice of Cynanchum ovalifolium yields Caoutchouc at Penang. 

 Marsdenia tenacissima and Orthanthera viminea, East-Indian plants, afford 

 very tenacious fibre ; Marsdenia tinctoria a kind of Indigo. The Stapelice 

 and Ceropeyice are remarkable for their succulent habit ; some of them 

 form curious tubers, as Brachystelma. Hoya partakes of the succulent 

 habit, but has wax-like leaves and blossoms, sometimes very handsome. 

 Dischidia is remarkable for its pitcher-leaves. Gymnema lactifera is the 

 Cow-plant of Ceylon, which yields a milky juice, harmless and nutritious, 

 and which is used by the natives as food. 



HYDROPHYLLACEAE form a small Order, allied in some respects to 

 Boraginacese, but differing in their one-celled many-seeded ovary with 

 parietal placentation, which also separates them from Polemoniaceae, with 

 which they have many points of agreement. They are chiefly natives of 

 the north and extreme south of America. Their properties are unimportant ; 

 but species of some of the genera, as Nemophila, Eutoca, &c., are interesting 

 and showy garden plants, grown with us as tender annuals. Hydroleads 

 are sometimes separated from this Order by reason of their distinct styles 

 and anatropous ovules. 



DIAPENSIACE^J consist of two genera, Diapensia and Pyxidanthera, 

 each having one species. They are connected with Convolvulaceae by 

 some authors, but appear to stand between Hydrophyllaceae and Pole- 

 moniaceee, having a 3-celled ovary like the latter, and a filiform embryo 

 with very short cotyledons, approaching that of the former. They are 

 very closely allied to Ericaceae, but the anthers do not open by pores. 



POLEMONIACE^E (THE PHLOX ORDER) consists of herbs with 

 alternate or opposite leaves, regular o-merous and 5-androus flowers, the 

 lobes of the corolla mostly convolute (sometimes imbricated) in aestiva- 

 tion ; ovary 3-celled, style 3-lobed ; the capsule 3-celled, 3-valved, few- 

 or many-seeded ; valves usually breaking away from a triangular central 

 colunieila ; seeds perispermic ; embryo straight ; cotyledons elliptical, 

 foliaceous. Illustrative Genera : Phlox, L. ; Polemonium, Tournef. ; 

 Cav. 



Affinities, &c. One of the smaller Orders ; it is remarkable for its 

 3-celled ovary. It is nearly related to Convolvulaceae, Cobcea agreeing 

 even in the climbing habit; the ovary equally distinguishes it from these, 

 the Hydrophyllaceae, and the Gentianaceae, to all of which it has close 

 affinity. From Diapensiacese it differs in the regular calyx and insertion 

 of the stamens, as well as in the embryo. The seeds are remarkable in 

 many cases for hairs upon the testa containing a spiral fibre ; in Collomia 

 these expand elastically when wetted j in Cobcea they are short, broad, 

 and firm. The Polemoniaceae occur most abundantly in the temperate 

 regions of North and South America. Polemonium ceeruleum, Greek 

 Valerian or Jacob's Ladder, grows in the north of England, and is common 

 in gardens. The other genera furnish some of the favourite tender peren- 

 nial and annual herbaceous plants of our gardens. They have no im- 

 portant properties. 



