470 SEMI-CENTENNIAL OF TORREY BorANICAL CLUB 
affects gelatine sensitized by silver bromide, and also the optic 
nerves of insects." If such a theory has any basis in fact, it 
might be applied to the hairs of the stamens, and possibly also of 
the styles of Pontederia. 
There can be no doubt that the numerous insect visitors of the 
pickerel-weed seek it for the nectar it affords. It was at first 
supposed that this was secreted by the basal region of the perianth, 
but on examination of sections I found that the fleshy character 
of the tube is due chiefly to the presence of numerous air chambers 
separated by diaphragms much as in the stem structures, and that 
nothing like nectar-secreting cells can be detected there. In 
sections of the ovary, however, are found conspicuous epidermal 
cells lining the three slit-like cavities left by the incomplete fusion 
of the carpels (FiGs. 6, 8); these and one or two layers of cells 
beneath them stain deeply because of their rich protoplasmic 
contents and large nuclei, and there can be no doubt that they 
secrete nectar which flows freely from the open lower end of the 
narrow cavities to form an accumulation in the perianth tube. 
These secreting cells were indicated in the figures of Pontederia 
given by LeMaout and Decaisne* and by Wilson Smith,t but their 
significance was not discussed. Similar septal nectaries were 
discovered in 1854 by Brongniartl in several genera; their histo- 
logical development was more exactly studied by Saunders$; and 
their variety of form and phylogenetic development in many 
genera of the Liliales, Scitaminales, and Bromeliaceae have been 
more elaborately set forth by Schniewind-Thies. | 
Ovary sections of Pontederia show also several groups of cells 
whose large nuclei and abundant protoplasmic contents present 
practically the same appearance as those of the septal nectaries; 
ese groups of cells are found imbedded in the tissue of the an- 
terior carpel, and in the solid portion of the two anterior septa 
lying above the septal nectaries, which do not reach higher than 
* LeMaout et Decaisne. Loc. cit. 
+ Smith, R. Wilson. A contribution to the life history of the Pontederiaceae. 
Bot. Gaz. 25: 324-337. М. 26: f. $4. 1 
Brongniart. émoire sur les glandes nectariféres de l'ovaire dans diverses 
familles de plantes monocotylédones. Ann. Sci. Nat. Bot. IV. 2: 5-23. 1854. 1 
$ Saunders, E. В. On the structure and function of the septal glands in Knip- 
hofia. Ann. Bot. 5: 11-25. 1800. 
|| Schniewind-Thies, J. Beitráge zur Kentniss der Septalnectarien. 1897. 
