2388 



ORCHIDS 



ORCHIDS 



2649. Structure of the 

 column of Paphiopedi- 

 lum Dormanianum. a, 

 a, anthers; b, body repre- 

 senting the third sta- 

 men; c, stigma. Under- 

 neath are the remains 

 of the floral envelopes, 

 which have been torn 

 away. 



The infection of the orchid embryo takes place 

 through the suspensor by means of which the embryo 

 was attached to the nutrient tissue of the ovule (Fig. 

 2654). From the suspensor the fungus invades the 

 cells in the lower region of the embryo, except the 

 epidermis. The cells become filled with dense inter- 

 woven gnarles of hyphae like those 

 in the roots. The coils in the 

 inner cells undergo a process of 

 digestion, but those in the outer 

 cells remain intact and send 

 hyphae through the root-hairs of 

 the papillae into the soil. New 

 papillae with long absorbing 

 hairs are soon developed and 

 the cotyledon and leaves begin 

 to be differentiated. After three 

 to four months, roots are pro- 

 duced and the young embryo 

 begins to assume the characteris- 

 tic form of an orchid seedling 

 (Fig. 2655). 



From these facts it is apparent 

 that for the growing of orchid 

 seedlings it is absolutely essential 

 that an association of the seed 

 with the proper root-fungus be 

 brought about. In practice, this has often been accom- 

 plished by the sowing of the seeds on pots containing 

 the parent plants. This method, however, has many 

 disadvantages. The plants cannot be repotted while 

 the seedlings are growing, and the seeds are likely to 

 be washed away in watering, since they cannot be 

 readily protected by a proper covering. Better suc- 

 cess can be secured by the use of straight-walled glass 

 jars with loose glass covers. These are filled with finely 

 chopped sphagnum, which is well pressed into the jar. 

 The whole is then sterilized in a steam-box for one hour 

 on three successive days in order to kill bacteria and 

 spores of molds which are likely to overrun the seed- 

 lings. After sterilization, the jars should be allowed to 

 stand for a few days. Those in which molds develop 

 should be discarded. The sterile jars may then be 

 inoculated with the root-fungus from the species of 

 orchid to which the seed-plant belongs. 

 For this purpose, portions of infected roots 

 should be cut into small 

 pieces with a sterile knife 

 and scattered over the 

 sphagnum seed-bed. 

 Great care should be ob- 

 served at all times to 

 avoid the introduction of 

 foreign spores from the 

 air. It should also be 

 borne in mind that only 

 the covered roots contain 

 the fungus, and that gener- 

 ally only the soft tissues 

 from Yi to 1 inch back from the root-tip are most 

 abundantly infected. As soon as the root-fungus has 

 grown through the sphagnum, the seeds should be 

 sown in the jars. In the collection and handling of the 

 seeds, all possible precaution should be taken to pre- 

 vent contamination. 



While the difficulties involved in these manipulations 

 are considerable, they are not insurmountable, and it 

 is not unlikely that in time means will be found to 

 remove many of the uncertainties which at present 

 attach to the growing of orchid seedlings. With the 

 increasing demand for orchids for cut-flowers and for 

 general florists' use, and the depletion of the sources of 

 supply of imported orchids, especially of the rarer 

 endemic varieties, the growing of seedlings will 

 become more and more a matter of necessity. The pro- 

 duction of new and improved varieties, and the preser- 



2650. The pendent anther in 

 Coelogyne speciosa. 



td> 



2651. Column of Phaius 

 cupreus. h, cavity below 

 the anther; /, filament; p, 

 pollinia; cd, caudicle; r, 

 rostellum; n, stigma; w, 

 petaloid extension of the 

 dorsal part of the column 

 continuous with the lat- 

 eral wings, rd. 



vation and multiplication of rare sorts will be greatly 

 facilitated when the growing of seedlings is freed from 

 its many uncertainties. The seed-grown plants have 

 many advantages over the imported ones. They are 

 from the start better adapted to greenhouse conditions. 

 They are hardier and more resistant and can be grown 

 into plants of better form. They also flower more freely 

 and often can be made to bloom twice a year. 



Hybrids. 



One of the most fascinating phases of orchid-culture 

 is the production of hybrids. By the crossing of differ- 

 ent genera and species, numer- 

 ous new orchids have been 

 produced, many of which are 

 superior to the native species. 

 The first orchid hybrid to be * 

 produced in cultivation was 

 Calanthe Dominii, a cross 

 between C. masuca and C. fur- 

 cata. It was raised by Mr. 

 Dominy in the nursery of 

 James Veitch & Son, and flow- 

 ered in 1856. Other hybrids, 

 including the beautiful Calanthe 

 Veitchii, appeared in the fol- 

 lowing years, and in 1861 the 

 same grower produced the first 

 bigeneric hybrid, Goodyera 

 Dominii, which was a cross 

 between Hsemaria (Goodyera} 

 discolor and Dossinia marmor- 

 ata. Since that time the inter- 

 est in orchid hybridization has 

 grown greatly. The number of 

 orchid hybrids now is between 3,000 and 4,000. Rolfe 

 and Hurst record twenty-three genera which have en- 

 tered into bigeneric hybrids, and many cases in which 

 three genera have entered into the hybrid. In some 

 hybrid genera, like Lseliocattleya, the forms far out- 

 number the species of the parent genera. 



The pollination of orchid flowers requires a little 

 skill and patience and a knowledge of the parts of the 

 flowers described earlier in this article, but otherwise 

 offers no great difficulties. Only strong and vigorous 

 plants should be chosen for seed-bearing, since the pro- 

 cess greatly exhausts the plant and sometimes even 

 causes its death. The pollinia are mature and the 

 stigmas are receptive when the flower is fully open. 

 When it is the purpose to produce hybrids, it is well 

 to remove the pollinia of the plant that is to bear the 

 seed since the possibility of accidental interference by 

 the plant's own pollen is thus prevented. Even when 

 it is intended merely to grow non-hybrid seed, this 

 course is to be recommended, since, in nature, the 

 orchids are habitually cross-pollinated. The pollination 

 is easily accomp- 

 lished. To this end, ^I^^L 

 the pollen -masses 

 are removed from 

 the anther by means 

 of a sharp lead- 

 pencil or a pointed 

 stick and placed on 

 the stigmatic sur- 

 face. In the Cypri- 

 pediums and related 

 genera, the pollen- 

 masses are exposed, 

 but in most of the 

 other orchids the 

 pollen is covered 

 by the anther, which 

 can be readily re- 

 moved. The pollinia 

 can be picked up by 



K 



2652. J, column of Cochlioda san- 

 guinea; w, dorsal extension of column; 

 /, filament; p, pollinium; co, extension 

 of filament; sp, stipe; g, adhesive disc; 

 z, disorganizing tissue by means of 

 which the stipe and adhesive disc are 

 separated from the rostellum. K, two 

 pollinia with stipe and adhesive dis:; L, 

 lateral view of same. 



