Bot.— Vol. I.] CAMPBELL— SPARGANIUM. 295 



saturated alcoholic solution of picric acid, saturated alco- 

 holic corrosive sublimate, and weak Flemming's solution 

 were employed, but of these the corrosive sublimate, on 

 the whole, proved most satisfactory. The material was 

 imbedded in paraffin and the sections were stained, usually 

 with a double stain of Bismarck-brown and safranine, 

 although in some cases they were stained in toto with alum- 

 cochineal before they were imbedded. 



I. The Flower. 



All of the species of Sfarganium are monoecious, both 

 staminate and pistillate flowers being aggregated in dense 

 heads which are either sessile or borne on short pedicels. 

 The lower heads are always pistillate and the upper ones 

 staminate. The latter are usually much more numerous. 

 In S . simplex and its allies the main axis is unbranched, 

 while in the other species, e. g., S. eurycarpum and S. 

 Greenii, the stem is branched. 



Both sorts of flowers are exceedingly simple in structure. 

 The individual flowers are borne in the axils of small bracts, 

 and are themselves surrounded by a varying number of 

 small membranous leaves which are usually considered to 

 represent a very simple perianth. The male flower is com- 

 posed of three or more stamens, while the female flower 

 has either a single carpel, as in S. simplex, or a compound 

 pistil composed of two completely united carpels, as in S. 

 ramosum or S . Greenii. 



The development of the flower has been studied to some 

 extent in S. ramosum (Dietz, 1887), and is briefly as fol- 

 lows: Upon the primary axis are borne elevations which, 

 in the lower part of the axis, where they are produced 

 in axils of leaves, may develop into secondary axes, 

 but in the upper portions of the axis, form at once the 

 young inflorescences. In S. simplex and its allies, this axis 

 does not branch, and all of the lateral axes develop into 

 heads of flowers. 



