THE OVULE OF IMPATIENS 197 



The primordia of the mteguments, or at least the inner one, 

 are present as soon as the o\'Tile becomes distinct from the pla- 

 centa, but their differentiation from the nucellus is not apparent 

 until after the archesporial division. The average thickness of 

 the integuments is about equal to that of the nucellus, which 

 consists of five rows of cells. The ovule being anatropous, the 

 outer integument is missing on the side next to the funiculus. 

 Both integuments grow to equal length, and are prolonged far 

 beyond the nucellus so that the embryo-sac lies near the center 

 of the ovule (fig. 1, H). 



Longo, in his paper on the Asiatic species of Impatiens refers 

 to a large number of authorities, all of whom agree in the state- 

 ment that Impatiens has two integuments. It is clear that I. 

 pallida has two, and judging by Longo's figures, they are very 

 similar in form to those of the species I, amphorata, but different 

 from those of /. roylei. In the latter, the outer closes over the 

 tip of the inner. 



The innermost layer of the inner integument is composed of 

 broad, flat cells forming a heavy tapetal jacket (fig. 1, I and J) 

 similar to that which Chamberlain describes ior Aster novi-angliae. 

 As in the latter plant, these cells line the micropyle for a short 

 distance, and are clearly a part of the integument. Such a jacket 

 has been found in Helosis,^ Sium, Campanula, in the Scrophulari- 

 aceae, and the Stylidaceae. It is evidently characteristic of the 

 higher forms of Dicotyledons. 



The nucellus consists of five straight rows of long slender cells 

 with pointed ends, resembling tracheid cells (fig. 1, J). This 

 phenomenon has been observed in a number of plants, e.g., 

 Casuarina, Castania and Asclepias, and is interpreted by Coulter 

 and Chamberlain as suggesting a relic of their function as nutri- 

 tive cells. The fact is more striking in /. pallida in that the 

 chalazal cells immediately above the nucellus are of the same 

 form, and a definite core of these cells may be distinctly seen 

 and traced back until they join the tracheids in the funiculus 

 (fig. 1, H). 



• ■* Coulter, J. M. and Chamberlain, C. J., Morphology of Angiosperms. New 

 York, 1909. 



