The Gametophytes of Calopogon

Lula Pace
1909 Botanical Gazette  
Photolith plates 2nd edition This paper reports a continuation of the work on certain orchids begun in i906. The peculiarities in the development of the megaspores, and in the number and origin of the nuclei in the embryo sac found in Cypripedium (I4) made it seem desirable to continue the investigation. The same methods were used as in the work on Cypripedium. The material of Calopogon pulchellus R. Br. was collected near Chicago in the summer of i9o6. The usual chromacetic and alcoholformalin
more » ... and alcoholformalin solutions were carried to the field and the material was killed as collected. The greater part of it has been cut in serial sections five to seven microns thick, and stained in safranin and gentian violet. MEGASPORES The ovules are very numerous and even smaller than those of Cypripedium, the mother cell being five to ten microns in diameter. The archesporium does not seem to be differentiated early. Fig. i shows an ovule pretty well advanced, and yet it is not possible to distinguish an archesporial cell by any difference in staining. The one drawn shows the greatest difference in size in favor of the usual archesporial cell, but other ovules in the same ovary show the other cells of the axial row to be larger; so here also it is probably the cell that is approaching mitosis that is larger. Fig. 2 is taken from another ovary in which the ovules are apparently in the same stage as in fig. i . This one suggests a more advanced stage by the broadening of the ovule. Yet this may be related to the appearance of more than the one mother cell, for these ovules with two sporogenous cells are broader, as will be seen later. The first undoubted archesporium seen was in the stage shown in fig. 3 . Here the ovule is much larger than in the first two figures and the first integument is beginning. In this ovary more than half of the ovules were in this stage, the archesporial cell being large and showing difference in staining reaction. Botanical Gazette, vol. 48] [I26
doi:10.1086/329973 fatcat:6hhcitp5orfuvfulgy36unmbfa