233 



with Mr. Joseph Schrenk,* who observes " there is no reason why 

 we should separate these two organs and call them two different 

 flowers, when, in fact, they could not be any more closely con- 

 nected than they really are." In the perfect flowers the stamens 

 are clearly hypogynous, proceeding, as Mr. Schrenk states, from 

 the same vascular bundle of which that of the pistil is a branch. 



The flowers in most of the aquatic species are enclosed in a 

 pair of small falcate or semilunar membranous bodies, which are 

 by most authors termed bracts, by some a perianth, and by Mr. 

 Schrenk in the article referred to floats. It is not easy to decide 

 certainly upon the office of these bodies, but the explanation of Mr. 

 Schrenk is ingenious and has several good reasons in its favor. That 

 they are sacs containing air is evident. They are also most vig- 

 orous in the rosette of floating emersed leaves, where they would 

 be of most service if really intended to impart buoyancy to the 

 plant, decaying or shrivelling as the stem elongates. Another 

 thing which seems to confirm this theory is the fact that they are 

 wanting in the terrestrial species, but then, on the other hand, 

 this is equally true of ^. aiitumnalis, which is entirely submerged. 

 Whatever may be the truth in regard to these bodies, we may 

 properly speak of them as perigonial sacs. 



As a rule, the flowers of Callitriche are diclinous, consisting of 

 a single stamen or a single pistil, but in some species they will be 

 either all perfect, or, whenever the stamen is lacking, two pistils 

 in the same axil. Filaments elongated ; anthers reniform, two- 

 celled, dehiscing by side slits which finally flow into one across 

 the top. Styles two, filiform, papillose. Fruit sessile or on peduncles, 

 which in some species are greatly elongated at maturity, corn- 

 pressed, four-celled, more or less winged or keeled on the mar- 

 gins, four-lobed, the lobes united in pairs so as to form two discs 

 with a groove between them, separating at maturity into four 

 flattish carpels, each containing a single seed. 

 Fruit pedunculate. 



Perigonium none. 



Peduncles minute, \-\ mm. long. 



I. C. deflexa, var. Austifii. 

 * See his article in Bot. Gaz., 13, 296. 



