177 
at left a sporangium with a single small sterile cell at the top and at right an 
apparently terminal sporangium. There is no doubt that the sporangia here men- 
tioned are transformed cells of the filaments in which they are situated; this is 
more doubtful in the case represented in 
fig. 95 J, where the sporangium has the 
appearance of being lateral, but as it has 
been found in the same crust as those 
figured in fig. 95 FH, it must be sup- 
posed that it has really been terminal. 
The single sporangia are 2 to 3 times as 
long as broad, 26—50 » long, 11--14 u 
broad. Their great length depends pro- 
bably on their terminal or subterminal 
place, which permits them to develop 
unhindered by sporangia or sterile cells 
lying above. In some crusts only such 
‘lengthened sporangia, singly or in pairs, 
are found; in others they are found in 
company with the ordinary seriate ones, 
as a rule, however, in different parts of 
the frond. By this fact it is shown that 
the two kinds of sporangia really belong 
to the same species. Single sporangia 
have been met with in three places in 
spring (Ks: Hastens Grund; Sa: Ronnen - 
in Begtrup Vig and Lb: off Middelfart). 
There is no resemblance between 
the single sporangia of this species and 
those of Petrocelis cruenta J. Ag., which 
are strictly intercalary and globular (comp. 
LE JoLıs Alg. mar. Cherb. pl. III, fig. 4). 
In specimens gathered in November 
in the Great Belt I have found spores 
germinating in the seriate sporangia (fig. 
95 E). The spores were divided by va- 
riously orientated walls and some of the 
uppermost resulting cells were growing 
out upwards into filaments. 
The antheridia arise in the upper 
part of the vertical filaments, where they 
form small lateral bushes, rather similar 
Fig. 95. 
Petrocelis Hennedyi. Vertical filaments with tetrasporangia. 
A, six still undivided sporangia, November. B and C, 
ripe sporangia, July. D, filament with two sporangia 
only, April. E, tetraspores germinaling in the sporangia, 
April. F-I, from Begtrup Vig, May, F with seriate spor- 
angia, G with subterminal, H and I apparently with 
terminal sporangia (in J possibly lateral ?). A,D,E,G,H 
390:1 B,C,F, I, 300: 1. 
to those of Cruoria. They are borne on 
the upper end of small, usually unicellular, more rarely bicellular, branchlets, two 
D. K. D. Vidensk. Selsk, Skr., 7. Række, naturvidensk. og mathem, Afd. VII. 2, 
23 
