ONCIDIUM 



ONCIDIUM 



2341 



range in size from small erect forms, scarcely 6 in. in 

 height (O. pumilum}, to those resembling 0. altissimum, 

 with immense climbing panicles 9-12 ft. high and cov- 

 ered with numerous medium-sized fls. The prevailing 

 color of the fls. is yellow, spotted and barred with 

 brown. White or rose-colored fls. occur in a few rare 

 examples (0. incurvum, O. ornithorhynchum). 



As a class, oncidiums are short-lived under cultiva- 

 tion. Few growers succeed in maintaining them in 

 good condition for any great length of time. The stock 

 is constantly renewed from the tropics. 



Cultivation of oncidiums. 



The genus Oncidium embraces a great number of 

 species which are found growing under such peculiar 

 and varied conditions in their native homes that imita- 

 tion of the same is usually impracticable and often quite 

 impossible. A fair degree of success, however, may 

 be obtained by careful observation and distribution of 

 the exceptionally difficult species among the several 

 orchid departments. 



The Sarcoptera section, which embraces such species 

 as 0. Cavendishianum, O. Lanceanum, 0. luridum, 0. 

 pulvinatum and others of similar structure, and the 

 O. PapUio section, with O. ampliatum, may be suc- 

 cessfully grown in a bright warm portion of the 

 cattleya department in small baskets suspended from 

 the roof, using for a compost a mixture of clean chopped 

 peat and sphagnum moss, freely interspersed with 

 lumps of broken charcoal. 0. cucullatum, 0. incurvum, 

 O. macranlhum, O. ornithorhynchum, 0. Phalaenopsis, O. 

 varicosum, with a few others of like nature, do well 

 under treatment similar to that given for odontoglos- 

 sums, which see. 



When a good collection of species is cultivated, a 

 large number, including many of the above, can be 

 readily grown in one house if it be especially adapted to 

 them. Such a house should be a span-roof structure of 

 east and west exposure, at an angle of about 40, which 

 will admit the longest possible light. The early morning 

 and late afternoon sun striking the glass at right angles 

 produces and prolongs the natural sun heat for a greater 

 part of the day, while at midday, when the outside 

 temperature is highest, the sun's rays strike the glass 

 obliquely, giving less heat, with little danger of the 

 plants becoming sunburned from lenses in the glass. 

 Oncidiums require more sun and air than most orchids. 



The benches may be of either wood or stone, and 

 should be covered an inch or two in depth with sand, 

 ashes or gravel. The benches and paths should be wet 

 down once or twice daily to insure a moist atmos- 

 phere. Ventilators should be arranged on both sides of 

 the roof: air may then be freely admitted without caus- 

 ing direct drafts on the plants by using the ventilators 

 on the sheltered side. In winter the temperature should 

 range from 50 to 55 F. at night and 60 to 65 by 

 day, or a few degrees more with sun heat and ventila- 

 tion. In summer it must be kept as low as outside con- 

 ditions will permit. From March until October, sha- 

 ding must be applied to the glass sufficiently heavy to 

 keep down the temperature without excluding indirect 

 solar influence. A good shading is made of turpentine 

 and white lead; it stands well and is easily removed. It 

 can be applied rapidly with a whitewash brush on a 

 long pole, and removed with a hard brush in the fall. 



Oncidiums may be grown in either pots or baskets, 

 but as many species are of rambling habit, the latter are 

 preferable. The tiny species, such as O. Limminghii, 

 do best on blocks with little compost beneath them. 

 Clean chopped peat fiber and live sphagnum moss, equal 

 parts, make the best general growing material, and 

 this should be liberally interspersed with broken pieces 

 of charcoal. The plants in all cases must be securely 

 fastened, and the compost must be pressed in moder- 

 ately firm, but should be used sparingly. Overhead 



syringing should be given frequently, about once or 

 twice a day in bright weather, but care must be taken 

 not to keep the compost too wet, for the roots are lia- 

 ble to decay: it is advisable to let them dry out occa- 

 sionally. 



Stock is increased by division or notching the rhizome 

 between the pseudobulbs just before the growing season, 

 allowing about three or four pseudobulbs to each piece 

 and separating the parts after the first growth is 

 matured. 



For other cultural notes on the genus, see the vari- 

 ous manuals on orchid-growing. 



ROBERT M. GREY. 



INDEX. 



SYNOPSIS OF SECTIONS. 



A. Lvs. plane, not terete. 

 B. Labellum smaller than the sepals and petals. . . 



Species 1-5 

 BB. Labellum at least as large as the other segms., 



often greatly exceeding them. 

 c. Lateral sepals more or less united at base. 



Species 618 

 cc.' Lateral sepals free. 



D. All the segms. having a distinct blade, 

 none of them linear-subterete. 



E. Pseudobulbs present Species 19-37 



EE. Pseudobulbs wanting or obsolete Species 38-44 

 DD. Only lateral sepals with distinct blade; 

 dorsal sepal and petals elongate, linear, 



erect, with an obsolete blade Species 45-46 



AA. Lvs. terete or subterete Species 47-48 



AAA. Lvs. subtriangular in section Species 49 



DESCRIPTION OF SPECIES. 



A. Lateral sepals united at base 1. micropogon 



AA. Lateral sepals free. 



B. Sepals and petals linear, flaccid. ... 2. phymato- 



[chilum 



BB. Sepals and petals broad, serrate. ... 3. serratum 

 BBS. Sepals and petals broad, entire or 

 subentire. 



c. Fls. brown 4. superbiens 



cc. Fls. yellow 5. macranthum 



1. micropdgon, Reichb. f. Pseudobulbs almost in 2 

 rows on the rhizome, broadly ovoid: Ivs. 4-6 in. long, 

 linear-oblong, rounded at the top, leathery: raceme 

 8-10 in. long, on a long stalk, flexuous, pendulous; fls. 

 \ l /i in. across; sepals linear-oblong, undulate, yellow, 

 barred with brown; petals clawed, orbicular, yellow, 

 with a deep red-brown claw; labellum yellow, smaller 

 than the petals, having 3 almost equal, rounded, clawed 

 lobes. Aug. Trop. Amer. B.M. 6971. Gt. 4:308. Var. 

 superbum, Hort., is advertised. 



2. phymatochilum, Lindl. Pseudobulbs broadly fusi- 

 form, 4-5 in. long, purplish brown, with several large 



