702 
Yendo.—The Development of 
Setchell 1 has found small clusters of hairs in Saccorhiza dermatodea , 
not only in the area of complex structure but also in the monostromatic 
part of the blade of some young specimens. In Costaria , the simplest 
structure provided with them, so far as I could ascertain, was not less than 
four layers of cells thick (Fig. 27, PI. LIV). Before the three ribs have been 
marked out, no indication of cryptostomata could be found either in the 
four-layered area or in the transitional region of more complex structure. 
I am inclined to think from this fact that the cryptostomata are formed 
in all parts of the blade, though there may be differences in structure, after 
a plant has attained to a certain stage of development. 
The primary haptere, after being formed in the manner before de¬ 
scribed, remains simple until the first three ribs have appeared. When the 
bullations begin to attract our notice, new rhizines are given off in a 
radiating manner above the primary one. These rhizines follow the growth 
of the frond to a certain extent, but mostly remain in the simple state. 
The new whorls of rhizines above the old ones grow and ramify to play the 
important part of the adult holdfast. 
Post-embryonal Stages. 
The appearance of the last pair of ribs may be taken as an indication 
that the embryonal stage of the plant has ended. At this stage, indeed, all 
the characters of the species that might be found in an adult frond are 
manifested, though in a primitive state. 
The further development of the fronds after this stage is practically 
in the internal structure. Every element which makes up the blade, stipe, 
and holdfast gradually adds to its thickness and becomes more complicated. 
The external characters undergo but little change except that the size 
of the frond gains in an enormous degree. The fronds which measure 
10-15 cm. at the end of December will attain to a total length of as much 
as i*5 metres by the beginning of April. Among the minor changes in the 
external characters, the appearance of the longitudinal furrows on the stipe 
and the gradual change in the shape of the base of the lamina are to be 
mentioned. 
As I remarked several years ago, 2 the general outline of the blade 
of a Laminariaceous plant undergoes gradual change by age. The important 
change is in the transitional region. Those species with a round or even 
cordate base of the lamina in the adult have, in a majority of cases, 
a cuneate or acute base while yet young. So also in the case of Costaria , as 
shown in Figs. 11, 12, PI. LIII, and Fig. 29, PI. LV. After a blade has 
been furnished with the five ribs, it begins to add to its length at a 
1 Setchell: Concerning the Life-History of Saccorhiza , p. 182. 
2 Yendo : Three New Marine Algae from Japan. Bot. Mag., Tokyo, 1903, vol. xvii, p. 101. 
