RoscndaJil : embryology of symplocarpus foetidus. 7 



naked in the cavity of the ovary without any protective layers or 

 seed coats (Fig. 28, PI. II). 



Summary. 



1. The inflorescences of Symplocarpus foetidus develop very 

 slowly and the rudiments of the flowers are distinguishable from 

 eighteen to twenty months before the time of blossoming. The 

 ovules are developed during the late summer and fall months of the 

 year previous to blossoming. In most cases the ovary is one-cham- 

 bered, with only one ovule in each chamber. The ovule is ortho- 

 tropous and pendant from the upper part of the cavity. Occasion- 

 ally two chambers are found with one or more ovules in each. 



2. A single archesporial cell is differentiated which becomes 

 the spore-mother cell. This, by two successive divisions, gives rise to 

 four megaspores. In most cases the two megaspores towards the 

 chalaza end lie in the long axis of the ovule, while the two towards 

 the micropylar end lie transversely. All four spores germinate, the 

 innermost one giving rise to the embryo-sac, the others breaking 

 down. 



3. The first divisions of the oospore are transverse and a row 

 of three or four cells is built up before anticlinal walls appear. 



4. In the development of the endosperm a brief period of free 

 cell formation is followed by the appearance of cell walls whereby a 

 tissue is built up throughout the embryo-sac. It grows rapidly and 

 encroaches upon the inner and outer integuments, and finally begins 

 to push back into the basal tissue of the ovule. 



5. The antipodal cells give rise to a tissue made up of a con- 

 siderable number of cells with greatly enlarged nuclei. 



6. The pro-embryo as it grows becomes at first club-shaped 

 and later on pyriform or ovoid. A short suspensor, consisting of 

 several rows of cells, is formed. Upon one side of the pro -embryo, 

 near the suspensor, a small depression appears, which later deepens 

 into a groove. On the axial side of this groove the leaves and 

 plumule are differentiated. 



7. The embryo, during its growth, completely consumes the 

 endosperm, together with the integuments and other ovular tissues. 

 Consequently it comes to lie practically naked in the cavity of the 

 ovary and hence no real seeds are produced in Symplocarpus foe- 

 tidus. 



