a oe 
is greatly more thin and delicate than that of U. datissima. The 
form of both plants is too variable to find a place among the dis- 
tinctive characters. U. datissima is found at all seasons and — 
on every shore; but U. /actuca is seldom seen except in spring 
or early summer. 
Fig. 1. Unva Lacruca, young and old plant:—the natural size. 2. Small 
portion of the membrane :—magnified. 
