A contribution to the life history of Uvularia sessilifolia 
ISABEL ALDEN 
(WITH PLATES 34, 35) 
INTRODUCTION 
That the seasonal development of any plant, especially with 
reference to the unfavorable winter season, should be of interest 
and of some significance is undoubted. Such a study has been 
begun here with Uvularia sessilifolia and includes field observa- 
tions as to growth of rhizome and aerial shoot as well as a more 
detailed study of the development of the megasporangium and 
microsporangium. The chronological development of these latter 
organs has received some attention, but the actual number of 
cases is meager, and what the significance of the history of these 
organs of reproduction may prove to be can be shown only after a 
considerable number of plants, particularly of related genera, have 
been studied. The variations thus far brought to light show the 
need of an even wider range of investigations in this line than at 
first would seem necessary. The plants that have been thus 
Studied so far show a wide range of variation. Symplocarpus 
foetidus (Duggar!) showed the nuclei of the definitive archesporium 
in a resting condition about October first, with the divisions of 
the pollen mother cells taking place the first warm days of April. 
In Trillium (Smith?) the microspores were found in the mother cell 
stage in April together with the four potential megaspores. In 
Hepatica (Chamberlain®), however, the early spring, that is while 
the ground was still frozen, showed pollen grains fully formed and 
the embryo sac ready for fertilization. The same investigator‘ 
Claimed that Salix passed the winter in the microspore mother cell 
Stage with no megaspore defined till after the renewal of growth 
in the spring. This condition of the microsporangium has been 
challenged, for Salix fragilis (Moore®) showed the cells of the 
anther stil] homogeneous without differentiation of tissue in 
vember. Perhaps Corylus and Alnus’ gave the most extreme 
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