678 HYDROPTEKIDKS. (mARSILIACE^..) 



1. MARSIlIA, L. Marsilia. 



Submersed or emcrscd aquatic plants, with slender creeping rootstocks, send- 

 ing up elongated petioles, which bear at their a|)ex a whorl of 4 nervose-veined 

 leaflets, and at or near tlieir base, or sometimes on tiic rootstock, one or more 

 globular but somewhat eccentric sporocarps. These sj)orocarps or fruit arc 2- 

 cclled vertically, and with many transverse partitions, and split or bur>t into 2 

 lobes at maturity. On the partitions arc inserted numerous short-stalked spo- 

 rangia, of two sorts intermixed ; the larger ones containing a single oval or ob. 

 long spore, the smaller containing many very minute spores. (Named for 

 Aloijsius Marsili, an early Italian naturalist, — therefore to be written IMarsilia, 

 not Marsilea.) 



1. M. quadrifblia, L. Leaflets broadly obovate-cuncate, glabrous ; spo- 

 rocarps usually 2 or 3 on a short peduncle from near the base of the petioles, 

 pcdicelled, glabrous or somewhat hairy. — In water, the leaflets commonly float- 

 ing on the surface ; Bantam Lake, Litchfield, Connecticut, Dr. T. F. Allen. 

 The only known habitat in America. (Eu.) 



2. M. uncinata, Braun., with luiiry leaflets, and villous short-stalked or 

 sessile sporocarps, solitary at the base of each petiole, will doubtless be Ibund 

 in the northwestern part of Wisconsin. It has been confounded with the very 

 similar M. vcstita. Hook and Grcv., of the Southwest. 



*2. AZOLLA, Lam. Azoll.v. (PI. 20.) 



Plant floating free, pinnately branched, clothed with minute imbricated leaves, 

 appearing like a small Jungermannia ; fructification sessile on the under side 

 of the branches, of 2 sorts. Sporocarps covered at first with an indusium of a 

 single diaphanous membrane, ovoid : the smaller kind opening transversely all 

 round, containing several roundish aniheridia? pelt^itely attached to the sides of 

 a central erect column : the large or fertile kind bursting irregularly, filled with 

 numerous spherical sporangia rising from the base on slender stalks, each con- 

 taining a few globular spores. (Name said to come from a^u), to dry, and oAXo), 

 to kill, being destroyed by dryness.) 



1. A. Carolini^na, Willd. Leaves ovate-obloiig, obtuse, sjireading, red- 

 dish underneath, beset with a few bristles. — Still water. New York to Illinois 

 and southward. Plant forming little mats on the water, G"-12" broad. 



SALvfNiA n.Vtans, L., Said by Pursh to grow floating on the surface of small 

 lakes in Western New York, has not been found by any other person, and 

 probably does not occur in this country. It is therefore omitted. 



