28 SOME AUTUMN DAYS IN IOWA 
many fragments of limestone rock, for this is a 
limestone slope and the gray masses of castellated 
rocks beautified by the bright green mosses jut out 
here and there between the trees every few rods. 
Prying out one of the pieces of rock one is surprised 
to see it practically a solid conglomerate mass of 
marine shells, of various sizes and shapes. Other 
pieces are tried with the same result. Here are the 
quaint little shells of the Devonian series, remind¬ 
ers of the time, many millions of years ago, when 
Iowa with many of the adjoining states was a vast 
warm sea. A little more investigation shows the 
evidences of the coral formation which rises at 
Rock Island, at Iowa City and here and there up 
northward into Buchanan county. Little coiled 
shells, like worms, cornet shaped tubelets, these 
and many others are all found either in this mass 
of rock or near-by. 
But the best of the discovery is a litle further 
along the river bank on a rocky open place which 
goes to the water’s edge. This was the only place 
anywhere in the vicinity last summer where grew 
the partridge pea (Cassia ch am a e crist a ). The 
plant was so beautiful in July that no one would 
have thought of looking to see what lay beneath 
it. It was one of the most interesting plants of 
the summer, with each of its leaves made up of ten 
to fifteen pairs of linear oblong leaflets, a cup¬ 
shaped gland beneath the lowest pair and the large 
