52 Barber . — On the Structure and 
development appears to be simple enough. The oval lamina 
becomes early split up (Fig. 3), and the wounds caused by 
the splitting are healed by the formation of a new epidermis 
over the exposed part. 
The lamina grows to a very large size, and in the mature 
plant consists of very many narrow-pointed segments. The 
plant is easily recognised as the largest European seaweed, 
and one whole plant is stated to be a sufficient load for a 
man to carry on his shoulders. The parts of the lamina, 
when spread, may measure from six to twelve feet across. 
Arrangement of Tissues. 
The increase in thickness of L. bidbosa appears closely to 
resemble that described for Durvillaea Harveyi by Graben- 
dorfer 1 . This member of the Fucaceae also approaches the 
Laminarias in the absence of the vegetative cell at its 
apex. The peripheral cells give rise to new cortical cells 
by the formation of tangential walls, thus having the character 
of a meristem rather than that of a true epidermis. It will, 
however, be found convenient to retain the term epidermis 
in the following descriptions. 
A similar increase in thickness seems to be present in 
other Laminarias, but in L. bidbosa the epidermal region 
appears to be the only one in which active cell-division 
can be observed to take place. One would naturally expect 
that, in the excessive development of one part of the stem 
attendant on the formation of the ridge, there would be in- 
dications of a rapid cell-formation occurring in the peri- 
pheral meristematic layer. Such, however, does not appear 
to be the case ; all that is seen in section is a hemispherical 
expansion of the stem, and the outgrowth at this point 
seems to be due to the rapid increase in size of the cortical 
cells. In a section through this, or any other, part of the 
plant (Fig. 11), the epidermal cells are small and cubical, 
1 Bot. Zeit. 1885. 
