PAPERS ON BOTANY 159 
ness in shore floras is more general and of larger aspect. 
Among other causes, a water soaked compact soil by inhibiting 
root-development may have an important part. Especially 
significant in this connection is the permanent dwarfing of 
forms which hug the waters’ edge, such as some of the little 
water spearworts of the genus Ranunculus, or the genus Hy- 
drocotyle among the parsnips, or, more remarkable still, that 
of the family Salvinaceae amosg the Pteredophytes of which 
one representative, Salvinia, is aptly described as “floating 
like Lemna on the surface of stagnant waters,” and the other, 
Azolla, as “appearing like a reddish hepatic moss.” Finally 
this process of diminution reaches its consummation and ap- 
proaches most nearly the vanishing point among the Lemnacea, 
all of which are small, in the rootless and leafless Wolffia 
which in general appearance reminds one of Volvox rather 
than anything else, and the dimunitive Wolffiella which bears 
a close superficial resemblance to some of the low plankton 
algae such as Aphanizomenon. 
THE PRIMROSE ROCKS OF ILLINOIS 
H, S. Perpoon, LAKE ViEw HicH SCHOOL, CHICAGO 
The 9th day of April, 1905, the writer was tramping down 
the narrow, cliff-confined valley of the west branch of Apple 
River, spying out the bird life of this sheltered locality, and 
more than incidentally, keeping both eyes open for the early 
blossoms of Hepatica, Dicentra, Claytonia, Sanguinaria and 
Other bluff and valley species of plants. His attention was 
attracted to the peculiar coloration of a huge vertical cliff of 
limestone across and rising directly out of the river some fif- 
teen rods from the point of observation. The whole face of 
the rock for perhaps twenty feet vertically and extending 
fifty or sixty feet horizontally was a solid hue of pale laven- 
der purple. A “close up” inspection revealed thousands of 
small rosettes of delicate leaves, and springing from the center 
of each from one to four delicate slender scapes bearing from 
one to five small lavender colored blossoms. Only once before 
had any similar wild plants been encountered and they were 
the mealy primrose, growing on the rocky shores of Northern 
