ON STIPULES 35 



might mention Lathy ms, Genista, Passiflora, Acacia, 

 Spircea, Saxifraga, Rosa, Berberis, &c. in which some 

 species have stipules while others have none. 



While, then, in most families of plants the species 

 are all either stipulate or exstipulate, there are a good 

 many families in which the genera differ in this respect ; 

 some genera in which the species differ ; and, lastly, 

 there are some cases, even within the limits of a single 

 species, in which certain leaves are said to develop 

 stipules, and others to- be exstipulate, as for instance 

 Helianthemum guttatum, Ipomcea pendula, 1 Exocliorda 

 Alberti, &c. 



Let us now return to Vaucher's problem Why 

 should some species of Helianthemum have stipules, and 

 others not? and see whether we can find the answer 

 to it. 



Our common Helianthemum (H. vulgar e) has stip- 

 ules ; so have H. polifolium, H. tomentosum^ H. cegyp- 

 tiacum, H. rhodanthum, H. ciliare, H. lavandulcefolium, 

 and PI. rosmarinifolium. On the other hand, there are 

 a number of species which have no stipules : H. velandi- 

 cum, H. lasianthum, H. ocymoides, H. formosum, H. 

 Libanotis, and others. Now, in H. oelandicum (fig. 23) 

 the plant is dwarf and prostrate ; the leaves are opposite, 

 oblanceolate or spathulate, tapering to a broad base, 

 sessile, ciliate, especially at the base, which also widens 

 so as closely to ' sheathe the young bud, thus effectually 

 1 Choisy, in De Candolle's Prodromus, ix. p, 387. 



