706 
Yendo.—The Development of 
cells than the deeper-seated layers. He seems to believe all the layers 
to have originated from the same meristematic one, and he regards the 
above-mentioned differences as indicating that the growth of the stipe 
by formation of new cells is exceedingly slow. 
In the young blade of Undaria I have noticed the transverse division 
of the well-defined epidermal cells in a plane parallel to the surface. The 
daughter-cells form a discontinuous stratum of cells under the epidermis ; 
they are nearly equal in size to their mother-cells and much smaller than 
the pre-existing cortical cells. The latter are precortical cells or their 
derivatives. As the epidermis of the blade is a layer well defined from the 
beginning, the name ‘ limiting layer ’ cannot be applied to the resulting layers 
of Undaria without modifying Setchell’s conception. The name ‘Rinde’, 
again, when applied to the tissue of the blade, comprises two distinct parts, 
one originating from the precortical and the other from the epidermal 
layers. Similarly the ‘ cortex ’ comprises the cells interposed between the 
epidermis and the medulla whatever may be the difference in their origin. 
The distinction of the cortex into outer and inner layers as proposed by 
Setchell in the case of the blades of Saccorhiza comes near to separating 
the tissues according to their origin. 
Considering the origin of the glandular cells with reference to these 
conceptions, it may be advisable to modify my former statement concerning 
this point, as follows:—Each glandular cell, as a rule, originates from 
a subepidermal cell which has been generated from the epidermal cell 
above it. 
The cryptostomata are produced from the epidermal cells after the 
glands have appeared. Their number is far less than that of the glands. 
On examining the mode of development of the cryptostomata, I cannot find 
any essential difference from what has been seen in Costaria , At aria , 1 and 
Saccorhiza . 2 At the start, the position of the hairs is at the depth of one 
epidermal cell and is slightly depressed below the surrounding level. There 
is no special initiating cell comparable with that characterizing the Fucaceous 
cryptostomata (Fig. 35, PI. LV). 
The young blade of Undaria increases in area, adding the glands and 
cryptostomata proportionately. The appearance of the rachis takes place 
after the blades have attained at least 4 cm. in length. The primary rachis 
is constructed by cell-aggregation along the median line of blade. The 
origin of the cells is similar to that in the case of Costaria , but on both sides 
instead of one. The rachis is, of course, more sharply defined near the 
transitional region and gradually evanescent above. Such a stage of the 
plant is hardly distinguishable from the young lamina of Alaria , unless the 
presence of glands is taken into account. 
3 Murray: 1 . c., Plate XVI, Fig. 5-7. 
2 Murray 1 1 . c. 
