281 
haploid, and the diploid phase is restricted to the undivided zygole cell. To these 
Florideæ belongs, among the species mentioned in the present paper, Halarachnion 
ligulatum. Gloiosiphonia capillaris must also be haplobiontie on the coasts of Den- 
mark, where, as on those of France, tetrasporangia-bearing plants have never been 
found, though they have been met with on the coasts of Norway and Sweden 
(see p. 278). 
On the other hand, there are species which only propagate by tetraspores, 
not sexually. This applies first of all to the Hildenbrandia species, which are ex- 
tremely common with tetraspores, but have never been found with sexual organs. 
In Cruoriopsis gracilis also, and Rhododermis Georgii, sexual organs are quite unknown. 
Rhododermis elegans again, has always been found with tetrasporangia only, save 
for the case of some specimens from North-east Greenland, which bore antheridia. 
There are moreover some Corallinacee which have hitherto been found in Danish 
waters only with tetrasporangia (Lithothamnion lœve, glaciale, Sonderi, norvegicum, 
and lœvigatum). In all these, at any rate those first named, tetraspore formation 
must be supposed to take place without reduction of the chromosomes. 
It should further be noted that in some species, albeit possessing both kinds 
of spores, the two kinds do not occur with like frequency. This is probably the 
case with several of the Lithothamnion species just referred to, the sexual plants 
being presumably not altogether lacking, but merely rarer than those bearing tetra- 
spores, and have therefore not hitherto been found. On the other hand, sexed 
plants of Polyides rotundus seem to be far more common than the tetraspore plants 
in the Danish waters. All this might seem to suggest that these species have no 
regular alternation of generations, such as takes place in the typical diplobiontie 
Florideæ, in which sexual plants and those bearing tetraspores are nearly alike in 
point of frequency. 
Parthenogenesis has been shown with certainty in Platoma Bairdii by Kuckuck. 
In the Little Belt, it appeared in the same manner as at Helgoland, the antheridia 
lacking, whereas cystocarpia and tetrasporangia were found. Here also the tetra- 
sporangia must be formed without reduction of the chromosomes. Possibly partheno- 
genesis may also occur in other Cryptonemiales. Some observations would seem 
to suggest that this may be the case in Furcellaria fastigiata. The fact that I did 
not find the spermatia attached to the trichogynes I do not consider as of great 
importance; more significant, however, is the finding of an unfertilised carpogonium 
with a short trichogyne, but which had nevertheless formed an outgrowth which 
could only be regarded as a sporogenous filament (cf. p. 169, fig. 85 D). — In Petro- 
celis Hennedyi I found, in some instances, sporogenous filaments growing out from 
carpogonia which showed no interruption of the plasmatic connection with the 
trichogyne (fig. 98 E, 99 E) and here also, no spermatia were found attached to the 
trichogynes. 
Finally, some cases have been noted where tetraspores and sexual organs 
appeared in one and the same individual. This has occasionally been found in 
D. K. D. Vidensk. Selsk. Skr., 7. Række, naturvidensk. og mathem. Afd. VII. 2. 36 
