166 LETTER XLII. 



and projecting a little way beyond it. The ovary is 

 superior, contains three cells {Jig. 5.), in each of which 

 are about six ovules adhering to a placenta in the axis. 

 The style is thread-shaped, and terminated by three 

 narrow lobes {fig- 3.)- The seed-vessel (jig. 6.). opens 

 into three valves, bearing the dissepiments in their 

 middle. The seeds are spongy, oval bodies {fig. 7-)» 

 with a thick skin, and contain an erect embryo {fig. 

 8.) without albumen. 



If you contrast this with a Bindweed, you will remark 

 that in that plant, the corolla has its lobes plaited to- 

 gether, the stigma two-lobed, more or less, while here 

 the lobes of the corolla are imbricated, and the stigma 

 three-lobed. These distinctions are the most material 

 for separating the two tribes, for we cannot make 

 great use of the twining habit of the Bindweeds, first, 

 because Cobcea, which is of the tribe now under consi- 

 deration, also twines, and, secondly, because many Bind- 

 weeds do not twine. 



I have already adverted to the existence of a genus 

 called CoUomia ; it consists of species of little beauty ; 

 but in one of them, CoUomia linearis, the micro- 

 scope reveals one of the most marvellous phenomena 

 I am acquainted with. The seeds of this plant are 

 small, dry, hard and brown. If you look at them 

 ever so carefully while dry, you will find nothing that 

 can lead you to suspect the existence, in their skin, 

 of any peculiar mechanism. But place them under a 

 microscope, and, while watching them, gently float 

 them in water. In a few moments the fluid will appear 

 in rapid motion, thousands of silvery threads will be 



