FLOWERS OF IMP A TIENS FULVA 167 



of the sac. The generative nucleus takes a position alongside and 

 becomes much elongated (Fig. 14). 



V. The Pistil 



The early stages in the development of the pistil were referred to 

 briefly above. Three small prominences mark the origin of the pistil 

 (Fig. 5 A). These rise separately for a time, then the tissue rises as 

 a ring with more or less of a gap on one side and bearing the three promi- 

 nences on the top. The septa arise as five prominences pushing in from 

 the ovarian walls (Fig. 6). These prominences meet the rising placenta 

 and so divide the ovary into five chambers. Before the ovary has 

 closed over, one ovule generally has arisen in each chamber. These 

 arise laterally from the central placenta. This history suggests the 

 cauline nature of the ovules. Generally one ovule only arises in each 

 cavity, and five seeds is a common number in the mature capsule. 

 Before the ovule has reached the fertilization stage the septa show signs 

 of breaking down in their internal layers of cells (Fig. 34). This degen- 

 eration continues in later stages. 



At pollination the ovary is five-celled. The style is practically 

 absent. The stigmatic surface covers the upper and inner faces of 

 five little teeth on the top of the ovar\\ Near the bases of these 

 stigmatic teeth open the stylar canals. The stylar canals originate by 

 the failure of the ovary to close over completely in its upward stylar 

 prolongation (Fig. Zi). 



By the time the archesporial cell is clearly recognizable the inner 

 integument can be made out as a prominence on the side (Fig. 16). 

 Before the mother-cell has reached the synapsis stage, the inner integu- 

 ment has reached the top of the nucellus and the second integument is 

 indicated (Fig. 24). As in other anatropous ovules, the second integu- 

 ment is absent on the funicular side of the ovule. The second integu- 

 ment continues growth until it approaches the inner integument in 

 height. This condition is attained before the mother-cell has divided. 

 From this point onward the two integuments rise together. Hence 

 only at the tip are the two integuments to be distinguished. Below 

 the tip they are indistinguishable under the microscope. They are 

 not fused in the sense that two separate tissues have fused, but the 

 tissue below the tip arises as one continuous tissue. The layer of the 

 integument lying against the nucellus early becomes differentiated as 

 a zone of short broad cells apparently tapetal in function. This jacket 

 layer is remarkably persistent through the history of the ovule. It 



