Helianthemum. CISTACE/E. 151 



many-seeded : placentae filiform, in the axis of the valves or on iniperfuct 

 dissepiments more or less projecting into the cell. Embryo indexed. 



The North American species belong to the section Lecheoides, Dwnal ; havine 

 the exterior sepals minute, a very short straight style, and strictly parietal placenta;: 

 they are almost sufTruticose, with mostly stellular pubescence, and exstipulate slightly 

 petioled aUernate leaves, except the lowest, which are usually opposite ; and the evo- 

 lution of the (yellow) flowers is centrifugal. Excepting H. scoparium from Cali- 

 fornia, and II. Carolinianum, which hardly belong to this section, they dirter 

 from the European sjiccics in producing two kinds of (lowers: viz. 1st, Terminal or 

 dichotomal flowers, usually preceding the others, on slender pendunclca, with con- 

 spicuous petals and numerous stamens. 2nd, Smaller flowers, usually clustered in 

 axillary cymes or glomerules, scarcely ever fully expanding, witli minute petals or 

 often none, fewer stamens, and smaller and fewer-seeded capsules. The two kinds 

 often occur on the same specimens ; but the latter are produced later in the season, 

 and in sterile soil often to the exclusion of the others, giving to the plant the appear- 

 ance of Lechea, so much so as to have deceived Linnaius, wliose L. major is wel! 

 known to have been founded upon such a state of Helianthemum Canadense. Mr. 

 Spach has noticed this peculiarity in our species, and separated them as a distinct 

 genus under the name of Heteromeris. 



"r*"^!. //. Canadense (Michx.) : stem at first simple ; the primar}'^ or termi- 

 nal large and petaliferous flowers few or solitary, on peduncles scarcely longer 

 than the floAver, the erosely emarginate petals about twice the length of the 

 calyx ; secondary flowers axillary, very small, nearly sessile, solitary or some- 

 what clustered on short leafy branches, the petals very small or none, and 

 the outer sepals usually wanting ; leaves oblong or somewhat lanceolate, with 

 revolute margins (when dry), and, as well as the sepals and often the 

 branches and peduncles, canescently tomentose. — Michx. ! fl. 1. p. 308 ; 

 Pursh ! fl. 2. ]). 363 ; Ell. sk. 2. p. 4 ; Hook. fl. Bor.-Am. 1. p.72; Dar- 

 lingt. fl. Cest. p. 313. H. ramuliflorum, Michx. I. c. ; Pursh ! I. c. ; Ell. 

 I.e. li. coTymbosnm, Picrsh, fide herb. ! H. rosmarinifolium, P«rs/t .' I.e. 

 Cistus canadensis, Willd. ; Bigel. fl. Bost. ed. 2. p. 212. Lechea major 

 (the apetalous state), Limi. amcen. accul. 3. p. 11 (excl. fig.), fide Smith, &, 

 in herb. Gronov. f 



In dry sandy soils, Canada ! to Florida! June (April in the Southern 

 States) to Sept. — Stem 6-18 inches high. Capsules of the apetalous flowers 

 not larger than a pin's head, few-seeded : seeds angular, scabrous-punctate. 



,-J-^. H. polifolium, : primary or petaliferous flowers (small) terminating the 

 slender stem and the numerous short branches, on filiform peduncles many 

 times longer than the flower, the broadly cuneiform petals a little exceeding 

 the calyx ; secondary flowers very small, apetalous, 3-6-androus, clustered 

 in lateral cymnles on the floriferous branches, at first glomerate and nearly 

 sessile, at length on pedicels as long as the (.5-sepalous) calyx ; leaves linear 

 or linear-oblong, with revolute margins, beneath (as also the sepals and pedun- 

 cles) tomentose-canescent. — H. capitatum, Nutt. ! in herb. acad. Philad. 

 Heteromeris polifolia, Spach, in compan. to bot. mag. 1. p. 291. 



Prairies and dry sterile places, Arkansas, Nuttall ! Dr. Leavenivorth ! 

 and Texas, Drummond ! June-Aug. — Stem 9-12 inches high, minutely 

 canescent. Primary flowers polyandrous, usually solitary at the extremity of 

 the branches, scarcely half the size of those of H. Canadense. Seeds smooth 

 and shining, several in the petaliferous, but very few in the apetalous flowers. 



3. H. corymbosum (Michx.) : stem branching from the base, canescent ; 

 flowers in terminal fastigiate cymes ; the primary ones (rather large) on 

 filiform peduncles much longer than the flower, the petals nearly twice the 

 length of the calyx ; the secondary flowers in glomerate cymules, mostly 

 apetalous, 3-10-androus ; sepals tomentose-villous, the inner ones oblong- 



