1899] LIFE-HISTORY OF LEMNA MINOR 43 
growing point, and, although it has become free at the lower end, 
it remains closely appressed to the root (fig. 2k). An fige-7 
is shown a fairly young root in cross section, in which appears 
the temporary root sheath (a), the root cap (4), and the main 
body of the root (c), in 
which the axial region (d@) 
is more or less separated 
from the cortical region by 
air spaces. The cells of 
this axial region, which 
are three or four times the 
length of the cortical cells 
and not so wide, are ar- 
ranged with diagrammatic 
regularity about a central 
cell. The outer cells of 
this cylinder are seen to 
be dividing by periclinal 
walls. This axial cylin der Fic. 7. Cross section of young root. a, epider- 
is the representative of mal sheath. 4, root cap. c, body of root. d, axial 
the conducting system of ‘Y!inder X 1375- 
the root. The structure of the root is not unlike that of other 
water plants, e. g., naiads and potamogetons. 
My own observations and those of others have led me to 
Suggest that the lemna plant is not necessarily a flattened stem, 
in which the basal internode represents the original stem of the 
plant; or that it is a leaf with the power of producing new 
leaves from the specialized region known as the node; or that 
the basal region represents stem and the upper internode leaf; 
but rather that the entire structure is a shoot in which the basal 
and nodal regions are differentiated to serve special functions, 
and the upper internodes are entirely undifferentiated. The 
single conducting strand of the basal internode passes through 
the node and into the upper internode, where it may give off 
two branches, as in J. minor, or more, as in other species. It 
may also branch from the node into the new plants and the floral 
