138 The Botanical Gazette. [April, 
In the formation of the ribs of the ribbed forms, parts of 
what would be morphologically surface of the main stem, 
seem to take part, so that the raised pieces between the suc- 
cessive spine-clusters may be stem and not tubercle in their 
nature. Where is this true and where not? Only the most 
careful study, as to whether or not the leaves are laid down 
in actual contact at the vegetative point, can settle the mat- 
er. 
To be concluded, | 
Smith College, Northampton, Mass. 
