THE MARSILIAS. 197 



borne two or three together near the base of the 

 leaves. The common peduncle is about half an inch 

 long, with a short stalk for each sporocarp and is 

 usually united for a short distance with the petiole of 

 the leaf. In colour the ripe fruits are dark purplish 

 brown. When young they are clothed with minute 

 yellowish hairs, but at maturity these disappear. The 

 fruit is most abundant in shallow water. At the point 

 where the pedicel appears, to join the sporocarp there 

 project from it two small points called teeth. In this 

 species the teeth are very short and obtuse. There are 

 from sixteen to twenty sori in each sporocarp. 



Like the clover and oxalis, which it resembles, this 

 species has the habit of closing its leaves at night. This 

 is done by two of the leaves rising, folding face to face, 

 and then being enfolded by the other two in the same 

 position they had in the bud. The reason for this so- 

 called sleep position is doubtless to be found in the fact 

 that, like most water plants, the stomata or openings 

 for transpiration are found on the upper surface, and 

 this folding is in some way concerned with their protec- 

 tion. It is noticeable that only the young leaves or 

 those rising above the water display these movements. 

 When taken out of the water the leaves quickly close as 

 in the night position. Baker spells the specific name 

 qiiadrifoliata, but American writers do not. 



Marsilia Uncinata. 



Marsilia uncinata is commonly regarded as a rare 

 species, and in the latest edition of Underwood's text- 

 book it is recorded from but two stations in the United 



