CITRUS 
308 
For details see De Candolle’s Orig. of Cult. Pits . p. 176, or Treas. of 
Bot. 
Cladium P. Br. Cyperaceae (11). 40 sp. trop. and temp., esp. Austr. 
C. Mariscus R. Br. ( germanicum Schrad.), the only Brit, sp., is still 
abundant in Wicken Fen near Cambridge (the only bit of true fen 
now left), where it is cut as a crop. Formerly it abounded in the 
Fens and “was largely used for lighting fires at Cambridge and other 
places” (Babington). 
Cladrastis Rafin. Leguminosae (ill. 1). 1 sp. Japan &c., and 1 sp. E. 
N. Am. (cf. Epigaea). The wood of the latter (C. tinctoria Rafin., 
the yellow- wood) yields a yellow dye. 
Claoxylon A. Juss. Euphorbiaceae (A. II. 2). 40 sp. trop. Old World. 
Clarkia Pursh. Onagraceae (iv). 5 sp. W. N. Am. Favourite border 
plants. Mechanism of fir. as in EpHobium. 
Clausena Burm. f. Rutaceae (x). 15 sp. trop. Afr., Ind. , Austr. 
Clavija Ruiz et Pav. Myrsinaceae (1). 22 sp. trop. Am. Trees of 
palm-like habit (p. 155), often with firs, on the old wood (p. 156). 
Claytonia Gronov. ex Linn. Portulacaceae. 20 sp. N. temp, and 
arctic. Two have become naturalised in Brit. There are no stipules. 
Firs, in sympodial cymes. Before pollination the flower-stalk is 
erect; the fir. is protandrous, with outward movement of the sta. 
after dehiscence. Honey, secreted at the base of each petal, is acces- 
sible to short-tongued insects. After pollination, the stalk bends 
downwards through 180 0 , to return once more to the erect position 
when the fruit is ripe. The capsule contains 3 seeds and splits into 
3 valves, the seeds lying across the lines of splitting. The inner 
surfaces of the valves contract as they dry and shoot out the seeds (cf. 
Buxus, Viola; fig. in Ann. of Bot. 1892). 
Clematis Dill, ex Linn. (incl. Atragene L.). Ranunculaceae (3). 170 
sp. cosmop. C. vitalba L. (traveller’s joy) in Brit. Mostly climbing 
shrubs with opp., usually compound, leaves. The lower sides of the 
petioles are sensitive to contact. The petiole bends once round the 
supporting object, then thickens and becomes lignified (see p. 172). 
Firs, in cymes; calyx coloured; no petals or honey secretion. The 
style often remains persistent upon the fruit and becomes hairy, thus 
forming a mechanism for wind-distribution. 
Cleome Linn. Capparidaceae (1). 90 sp. trop. and warm temp. The 
disc is usually more developed on the posterior side and may bear 
scales. The gynophore varies much in length. In C. heptaphylla 
L. (?) there are two round shiny outgrowths at the base of the upper 
petals ; these look like honey drops even when not secreting, and may 
be compared with the “sham-honey” drops of Lopezia. The floral 
mechanism of C. requires investigation. 
Clerodendron Linn. Verbenaceae (iv). 90 sp. trop. and warm temp. 
C. Thompsonae Balf. is a favourite hot-house plant. It has a red 
calyx and white corolla. The sta. project so as to form the landing 
