156 THE PLANT WORLD 



airiount of growth in height per year being: ist year, ^ cm.; 

 2nd. year, 5 mm.; 3rd. year 5 mm. Toward the close of the 

 first year a few, not more than three, weak thorns were 

 produced at the top of the stem, and three more, but more 

 strongly developed (6 mm.) each succeeding year. A 

 branching of the root took place just below the surface of 

 the soil, a single tap root penetrating to some depth. 

 Secondary anatomical changes in the stem resulted in the 

 formation of the waxy bark, which, being fissured, exposes 

 the chlorophyll-bearing tissues of the cortex as in the mature 

 plant. 



Francis E. Lloyd. 



THE BOTANICAL GARDEN AT PISA. 



L^ncier the gulciance of Dr. Barsali I was able to spend 

 a few hours of an afternoon in late February at the ancient 

 Orto Botanico at Pisa, Italy. Leaving the broad riverside 

 street at the northern end of the Ponte Solferino, one pro- 

 ceeds northward along the Via Solferino, ciirectly toward the 

 Duomo, with the swinging lamp "of Galileo," and the famoiiS 

 leaning campanile. About a third of the way to the Piazza 

 del Duomo, on the right, are a group of grayish plastered 

 buildings which contain the laboratories and museums for 

 botany, zoology and mineralogy. A little farther 011 is :' 

 gate in the high wall which surrounds the botanical garden, 

 and a ring at the bell brings a smiling Italian portiere, who 

 opens the gate and shows one across the garden to the en- 

 trance to a liullding on the garden side. 



The garden is not large, being only about 250 meters 

 long and 7;; meters broad, but there is hardly a square meter 

 of it that is not used for the growing of plants. A large 

 portion of it is laid out in rectangular beds containing repre- 

 sentatives of the main families of flowering plants. At the 

 northern end are a group of small greenhouses with a mucii 

 crowded, but fairlv representati\-e collection of exotics. 



