A study of the somatic chromosomes of eight species of the Orchidaceae native to Minnesota was undertaken in 1931. Root tips were used, and were run into paraffin and stained with gentian violet. The diploid numbers were found to be as follows: Cypripedium acaule 20, C. pubescens 20, C. candidum 20, Calypsa bulbosa 32, Orchis spectabilis 42, Orchis rotundifolia 42, Habenaria bractiata 42, and Habenaria orbiculata 42. Sharp morphological differences were noted. The chromosomes of the cypripediums were very large measuring from 7-10 microns long, and from one to nearly two microns in diameter. Those of the other genera were much smaller. In Habenaria orbiculata, the chromosomes measured about 1½ microns long by about ½ micron in diameter. Considerable size variation was noted within each species.
Proceedings of the Iowa Academy of Science
©1932 Iowa Academy of Science, Inc.
Humphrey, L. M.
"The Somatic Chromosomes of Eight Species of the Orchidaceae,"
Proceedings of the Iowa Academy of Science, 39(1), 137-137.
Available at: https://scholarworks.uni.edu/pias/vol39/iss1/24