710 Yen do. — The Development of 
The latter, as in the case of Costaria above alluded to, result from the 
division of the pre-existing cells. The lower limit of the hyphal strands 
runs into the complex tissue of the transitional region. Judging from these 
facts, the hyphal cells seem to be added to the distal ones at the transitional 
region. They elongate to follow the extension of the surrounding area, 
keeping their original diameter. Hence, it may be understood that the 
primary septa of the hyphal filaments, at least in the embryonal stages of 
the blades, do not result from the division of the already completed hyphal 
cells. At a later period new hyphal cells may grow out as branches of the 
inner cortical cells, or the older cells may multiply by formation of septa. 
It is very interesting to note that the junctions of the hyphae are mostly at 
the intercellular spaces of the precortical cells ; and that the expansion of 
the terminal portion of the cell, to form the so-called trumpet cell, is already 
to be seen at such an early period of development. 
Taking the results obtained in Costaria and Undaria into account, it 
will be clearly seen that the sporelings of the Laminariaceous Algae start 
at first from a simple cell-row, then become monostromatic, distromatic, 
and so on, and finally proceed to the complex structure with hyphal tissue 
in the medulla. This accords satisfactorily with the conclusions arrived at 
by former investigators. One thing, however, remains to be remarked 
about the sclerenchymatous cells of Saccorhiza devmatodea which were 
termed ‘tubular cells’ by Setchell. 1 
Setchell 2 describes, in a very young blade of Saccorhiza dermatodca , 
a layer of the tubular cells interposed between the two epidermal, or, as he 
calls them, limiting layers. These tubular cells are, according to him, an 
important element of the medulla in the blade and stipe. He further 
describes a plant which has the first set of hapteres well developed. In it, 
at the tip of the blade, he finds ‘ a well-defined limiting layer on each surface, 
and within this, on both sides, a cortical layer of a single series of cells, and 
in the centre the medulla, represented by a few scattered tubes ’. 3 He has 
nowhere given any decisive information relating to the origin of either the 
tubular cells or the cortical cells. But it is possible to understand from 
what he describes in various parts of his paper, that he regarded them both 
as having originated from the epidermal layers. It naturally follows from 
his statements that the medullary elements at the beginning, and the cortical 
at the next stage, are generated from the primary epidermal tissue. 
The same writer attributes the origin of the hyphal cells to the ramifi¬ 
cations of the inner cells of the two- or three-layered cortex. This leads 
us to suppose that in Saccorhiza dermatodca the hyphal cells are developed 
at a somewhat later stage than in our plants. 
As in the case of Costaria and Undaria , the blades of the present 
1 Setchell : Concerning the Life-tiistory of Saccorhiza, p. 195. 
2 Ibid. 3 Setchell : 1 . c., p. 204. 
