1012 



DION^A 



DIOSCOREA 



1268. The Venus' Fly-trap 

 Dionaea muscipula. 



to continued and repeated stimuli caused by a caught 

 insect, or to chemical stimuli caused by its tissues, the 

 glands exude an acid and peptonizing digestive fluid 

 after a few hours; this starts digestive disintegration of 

 the insect's tissues, and the dissolved products are then 

 absorbed by the If .-halves: the fl. -stalk lengthens in 

 May to 8-10 in. and bears 4-10 white fls. which expand 

 in June, and which must be cross-pollinated for seed- 

 production. By the end of June the caps, burst, and 

 expose small black shining seeds. 

 These germinate in abundance 

 under a bell-jar on moist sandy 

 soil that is mixed with finely 

 chopped sphagnum moss. Each 

 seedling, after forming 2 lanceo- 

 late cotyledons, produces there- 

 after tiny fly-trapping Ivs. that 

 behave like the adult ones. 

 Plants thrive well when grown 

 in 3-5-in. pots amid a mixture 

 of fine silver-sand and black 

 silt. The pots should be kept 

 immersed for about an inch in 

 water, should have a slight top- 

 covering of sphagnum, and must 

 be kept near the glass in a green- 

 house with southeastern 

 exposure. Inhabits the 

 edges of moist sandy 

 savannah "bottom" 

 lands, is found wild over 

 a narrow strip of ter- 

 ritory about 10 miles in 

 width and 40 miles north, 

 also to an equal distance 

 south of Wilmington, N. 

 C., and grows well only 

 when the tips of its roots reach a moist substratum, and 

 when active transpiration proceeds. The perennial 

 underground part is a bulbous swelling that can 

 readily be dug and distributed from Nov. to March. 

 It is seldom that this wonderful little plant is seen 

 in a good state of cultivation any length of time after 

 removal from its native haunts. Its cultivation in a 

 greenhouse is usually attended with more or less diffi- 

 culty, owing to unsuitable conditions, such as too much 

 dry air, shade or unfriendly soil. It delights in full 

 sunshine, with a very humid atmosphere. When the 

 plants can be secured and transplanted with consider- 

 able of the soil in which they grow attached to the bulb- 

 like rootstalks, they are quite easily dealt with, and 

 may be kept in a healthy growing state for years. I 

 find a round hanging earthenware receptacle most 

 useful to grow them in; the bottom is carefully drained, 

 first with large pieces of broken pots, then smaller 

 pieces, and the upper layer is quite fine. Some chopped 

 fibrous peat is placed above this, when the plants are 

 built in with live sphagnum moss used to fill the 

 spaces between the clumps. Arranged in this way, it 

 is hardly possible to give them too much water, and 

 they revel in abundant supplies. If kept in the sun 

 the leaves take on a reddish tinge, but when grown in 

 the shade they are always green. Flowers will 

 develop about the middle of June, but they should be 

 nipped off as they make their appearance, for they are 

 apt to weaken the plant. The dionsea has been grown 

 successfully in a dwelling-house by a very different 

 method. The plants were in a wide, shallow dish, with- 

 out any drainage, and simply placed, not too firmly, 

 in loose live sphagnum moss, with a glass covering. 

 Water was given every other day by filling the space 

 above the plants until the dish was filled, and then it 

 was poured off. In this way the potting material 

 never became sour. From the luxuriant condition in 

 which these plants remained for years, I am inclined 

 to think this was a close imitation of the conditions 



under which they thrive in a wild state. Some years 

 ago, owing to Asa Gray's endeavor to have the Govern- 

 ment purchase a strip of land on which this plant 

 grows, there existed a widespread idea that it was 

 gradually becoming extinct. There seems to be little 

 likelihood of this calamity, however, as Dionsea is found 

 abundantly in some places. (G. W. Oliver, in Garden 

 and Forest, 10:237 [1897]). 



muscipula, Ellis. Fig. 1268. St. short, subterra- 

 nean, coated by the swollen bases of Ivs. : Ivs. 1-5 in. 

 long in radial rosette, divided into winged petiole and 

 bilobed lamina: infl. umbellate; fls. %-l in.; petals 

 white; stamens usually 15; pistil of 5 united carpels, 

 stigmas 5 penicillate: fr. a caps. B.M. 785. F.S. 3:280. 

 Mn. 1, p. 69. j. M. MACFARLANE. 



DIOON (Greek, two and egg; each scale covers two 

 ovules and the seeds are in pairs). Cycaddcese. Hand- 

 some foliage plants suitable for warm or temperate 

 palm houses and for planting in the open far South. 



This genus is said to be the closest to the fossil 

 forms of any living representative of the family. It 

 has the cones and twin seeds of Zamia and Encephalar- 

 tos, with the flat woolly scales of Cycas, but without 

 the marginal seeds and loose infl. of the latter. D. 

 edule has a flat rigid frond which is more easily kept 

 free from scale insects than Cycas revoluta, the common- 

 est species of the family in cult. A specimen at Kew had 

 a trunk 3-4 ft. high and 8-10 in. thick, the crown 

 spreading 8-10 ft. and containing 50 fronds, each 

 4-5 ft. long and 6-9 in. wide. Specimens of D. spinu- 

 losum are reported with trunk 24 ft. high. Both sexes 

 make cones frequently, the male cone being 9-12 in. 

 long and the female 7-12 in. The seeds, which are 

 about the size of Spanish chestnuts are eaten by the 

 Mexicans. There are a few species in Mex. Prop, by 

 seeds. Cult, same as Cycas. 



edtlle, Lindl. Lvs. pilose when young, finally gla- 

 brous, 3-5 ft. long, pinnatifid, rigid, narrowly lanceo- 

 late segms., about 100 on each side, linear-lanceolate, 

 sharp-pointed, widest at the base, rachis flat above, 

 convex beneath: male cones cylindrical, female cones 

 ovoid. Mex. B.M. 6184. G.C. III. 40:289. Gn. 55, 

 p. 365. Gt. 48, p. 157. Var. lanuginSsum, Hort., is a 

 very woolly kind. Gt. 48, pp. 154, 155. Variable. 



spinulosum, Dyer. Plants 6-50 ft. high, crowned by 

 a noble rosette of spreading Ivs. : Ivs. 4-6 ft. long, often 

 with 100 Ifts. on each side, these bearing 5-8 spines on 

 each margin. This is one of the tallest of all the cycads, 

 and is excelled only by the Australian Cycas media. 

 It is very unlike D. edule, which has a stocky trunk 

 and straight rigid Ivs. Mex. G.W. 4, p. 326; 5, p. 331. 

 A.F. 7:461. 



D. Dohenii, Hort. Discovered in mts. of Guatemala and named for 

 Edward L. Doheney of Los Angeles. Pacific Garden, Nov. 1912: 

 13. D. pectinatum, Hort. Like C. spinulosum: foliage described as 

 "very handsome, owing to the very numerous pinnae and their close 

 and regular arrangement. The texture is also firm and leathery, 

 with a sharp spiny point to each pinna." Gn. W. 24: 5. D. Pur- 

 pusii, Rose. Trunk short, crowned with numerous stiff and ascend- 

 ing Ivs. 3 ft. or more long; pinnse 2-4 in. long, sharp-pointed, entire 

 on the lower margin but usually with 1, 2, or 3 spine-like teeth 

 on the upper margin: male cones 6-8 in. long, the bracts with 

 recurved ovate tips; female cones ovate, about 18 in. long, the bracts 

 very woolly. S. Mex. WlLHELM MlLLER. 



L. H. B.f 



DIOSCOREA (Dioscorides, Greek naturalist of the 

 first or second century of the Christian era). Dios- 

 coreacese. Twining herbs from tuberous or thickened 

 rootstocks, grown as arbor vines or under glass for 

 the foliage, and also for the edible rhizomes and 

 aerial tubers. 



Type genus of a small family (of about 9 genera) 

 allied to Liliacese. It contains more than 200 widely 

 dispersed and confused species, most of them native 

 to tropical regions. Sts. herbaceous and twining or 

 long-procumbent, usually from a large tuberous root, 



