GERMINATION AND SEEDLING DEVELOPMENT IN FIVE SPECIES OF CYPRIPEDIUM L.

THE EFFECTIVE conservation of our native ladyslippers is in large part dependent upon an understanding of the reproductive habits and the environmental conditions necessary for population maintenance of the individual species. Such information is essential if proper management practices are to be undertaken, and even more essential if it should prove necessary in the future to resort to artificial propagation for the restocking of depleted areas. So far, no practical technique for the production of native ladyslippers by seeds or by vegetative division has been described. Many of the otlher species of niative orchids have been successfully raised from seed, in most cases by use of the general methods originated by Knudson (1922) for tropical orchids. The temperate zolne ladyslippers belong to the genus Cypripedium L. The seedling stages of only one of the twenty-eight known species have ever been described. Thilo Irmisch (1853) gave an excellent account of the seedling morphology of Cypripedium Calceolus L. , the solitary member of the genus occurring in Europe. The connected story of seedling development was pieced together by Irmisch from a series of seedlings discovered in the field. The earliest stage described was a protocorm "less than one line (112 inch) long . inverted, short cone slhaped, curved on the underside. " It assumed no regular position in the soil, being sometimes vertical, sometimes horizontal. Irmisch stated that neither the protocorm nor the roots possessed root hairs. The first leaf was scale-like, placed just above and usually on the same side as the first root. The elongating stem axis produced four or more nodes bearing scale leaves before the first true, chlorophyll-bearing leaf was produced. All but the first-formed scale-leaf possessed axillary buds. Fuchs and Ziegenspeck (1926) also gave descriptions of seedlings of Cypripedium Calceolus as determined from field-collected specimens. Their account agrees with that of Irmisch in most particulars. They differ in stating that the first root is exogenous instead of endogenous and that root hairs are present. Tropical ladyslippers of commercial importance belong to the distinct genus Paphiopedilum Pfitzer. Their seedling stages were well studied by Bernard in 1909. Their development, in part because of the 1 Received for publication November 9, 1942. Contribution from the University of Wisconsin Arboretum. Jour. Paper No. 3. This study was supported in part by the Research Committee of the University of Wisconsin and in part by a grant-in-aid from the American Association for the Advancement of Science through the Wisconsin Academy of Sciences, Arts and Letters. Special thanks are due Mr. Martin J. Gillen of the Gillen Wildlife Sanctuary, Gogebic County, Michigan, for the many courtesies and material assistance extended during the summers of 19391942. continual growth afforded by tropical conditions, is very different from that of Cypripediumn. Early studies by the author on asymbiotic anid symbiotic germination of native Wisconsin ladyslippers (Curtis, 1936) resulted onilv in the production of initial stages roughly resembling the protocorms described by Irmisch. Continued growth could not be maintained under tlle conditions then employed. It was felt that a knowledge of the enivironmnental conditions under which gerim-ination took place in nature would aid in the selection of methods for artificial germination. Accordingly, a study of seed production, seed germinationi, and seedlinig development of certain of the native ladvslippers was instituted in 1938. METHODS AND MATERIALS. Five species of ladyslippers are included in the study -Cypripedium reginae Walt. , C. acaule Ait. , C. parviflorum Salisb. , C. pubescens Willd. , and C. candidutm MNuhl. Seedlings of Cypripedium arietinum R. Br. were foLnd in 1924 in Door County, Wisconsini, in what is now the Ridges Wild Flower Sanctuary, but tlhev were not preserved and, hence, are not included in this studv. Locatiolns and dates of observation for the various species are shown in table 1.