428 MINNESOTA BOTANICAL STUDIES. 



Various characteristics have been used as the basis of iden- 

 tification of species; the leaves, their venation, their number, 

 the arrangement of the parts of the perianth, the colors, the 

 form of the essential organs and the divisions of the capsule 

 have all been considered. The seeds of native Orchids have 

 been examined and the forms found to possess distinguishing 

 features in each species. A number of the American Orchids, 

 including Cypripedium hirsutum Mill, have been studied by 

 Curtiss. By reason of the facts observed, he arrives at the 

 conclusion "that the ovules would by no means be an uncertain 

 element in the determination of species.'"" It is quite probable 

 that they would be less variable than other parts of the plants, 

 and holding, as they do, the germ of the plant, variations and 

 relationships might be more accurately determined. 



The embryo of Cypripedium calceolus L.^^ has been found to 

 be of an inverted conical shape, the upper surface being green- 

 ish or brownish. As the embryo develops, two delicate roots 

 appear at one side near the insertion of the first leaves which 

 closely sheath the germ axis. These primary roots are followed 

 by others which perform the usual function. A perennial axis 

 is formed in the first vegetative period, and an axillary bud is 

 developed. This is the bud which in the following year sends 

 up the flowering axis of the plant. 



Many propositions regarding the origin and relationship of 

 the genus have been brought forward, and the arrangement of 

 the parts has been worked out along this line. Although Rob- 

 ert Brown2 9 was the first to propose the theory of the fifteen 

 parts of the flower, other workers have more thoroughly sys- 

 tematized the matter. Darwin has given a diagrammatic repre- 

 sentation of the parts; the sepals forming the outer whorl of 

 the perianth, the petals, the inner whorl, the staminodium, the 

 only remaining part of the outer whorl of stamens, the two 

 fertile stamens in the inner whorl, and the three styles and 

 stigmas united into one. 



Masters^o has worked upon the floral conformation of Cy- 

 pripedium, and has "traced the nerves from the stalk of the 

 flower upward through the ovary and into the column. " The 

 arrangement was seen to be as follows: "Six vascular bundles 

 were found in one ring in the peduncle. Following these up- 

 ward, three were found to correspond to dorsal sutures of the 



(27) Curtiss, C.C. Contrib. Herb. Oolumb. Coll. 1:281. 1892. 



(28) Irmisch. T. Beitriige ziirBiolog. ilncl Morph. Orchid. '65. 1853. 



(29) Darwin. Fertilization of Orchids. 236: 1877. 



(30) Masters, M. T. Journ. Linn. Soc. Bot. 3a: 402, 1827. 



