426 The Ohio Naturalist. [Vol. VI, No. 3, 



The endosperm is continuous in the region of the embrvo but 

 in the lower end of the sac it forms only a thin layer. The later 

 divisions of the embryo are irregular; an oval mass of cells is 

 formed from the end of which the cotyledons develop. When 

 the embryo is about in the ten-celled stage walls begin to appear 

 in the endosperm (Fig. 20). Kirkwood found in Lagenaria 

 lagenaria and other species somewhat fiask-shaped embryos with 

 prominent end cells which correspond closely to those of the 

 same age in Cucumis (Fig. 21). 



The endosperm is not abundant but there is a greater amount 

 around the embryo than elsewhere, often the lower portion of the 

 embryo sac is entirely destitute of it. The endosperm stains 

 more deeply along the peripheral margin and around the embrvo 

 where the nuclei and starch grains are more abundant. The 

 embryo, however, takes the stain much more prominently than 

 any of the endosperm cells. 



The embryo develops a distinct layer of epidermal cells 

 before any cotyledonary protuberances appear (Figs. 23-24). 

 The embryo develops apically two cotyledons and distinctly 

 shows the root tip before there is any sign of the appearance of 

 the plumule (Fig. 25). The mature embryo sac contains only a 

 small amount of scattered endosperm, the main food for the 

 young plant being stored in the large cotyledons. In the 

 mature embrvo the plumule is two-lobed showing the incipient 

 first leaf (Fig'. 2G). 



The microsporangia appear to develop in the usual way from 

 a plate of hypodermal cells. The cells of the sporogenous tissue 

 are easily distinguished from the adjacent cells by their large 

 size, and different reaction to stains. The young anther shows 

 in cross section a single row of three microsporocytes in each 

 microsporangium (Fig. 31) ; but in longitudinal section the plate 

 shows a considerable length (Fig. 32). 



The mature pollen grain has a thick wall with a bulging at 

 opposite sides. The tube nucleus and generative nucleus lie to 

 one side of the grain near each other; the latter takes the stain 

 more deeply than the cytoplasm of the rest of the grain, due to 

 its denser structure. 



The behavior of the pollen tube in this species is of special 

 interest. It is large and distinct and with Delafield's Haema- 

 toxylin stains an amber color while the surrounding cells are a 

 purplish blue ; with other stains it is of a deeper color. It enters 

 the micropyle through the opening at the tips of the integuments, 

 pierces the beak of the nucellus and makes its way down to the 

 embryo sac by following a central path of much elongated clear 

 cells which seem to offer little resistance and serve as a definite 

 conducting tissue. The tube sometimes makes its way with 



