Classification of Green Algce. 119 
Sub-Family 3. Acetabulariese. 
Fertile and sterile leaves distinct, the sterile polytomously branched, 
fertile simple. Incrusted forms. 
[According to Solms-Laubach the apparent simple fertile leaves are 
in reality lateral branches of compound leaves of which the other 
branches are reduced or absent.] 
Genera. 
7. Halicorvne. Harvey, 1859. 
Stem bearing alternating whorls of sterile and fertile 
leaves, the former polytomously branched, the latter 
simple, lanceolate, slightly indexed, and producing a 
few strongly calcified aplanospores. 
8. Chalmasia, Solms-Laubach, 1895. 
Fertile leaves in a single whorl, calcified, partially 
connate to form a terminal disc. Aplanospores 
(gametangia?) few, calcified. 
9. Acicularia. D’Archiac, 1843. 
Fertile leaves wedge-shaped, in a single whorl laterally 
connate to form a terminal disc. Aplanospores 
(gametangia?) with lids, embedded in a calcareous 
homogeneous mucilage. 
10. Acetabularia. Lamouroux, 1816. 
Stem bearing successive whorls of polytomously 
branched, deciduous, sterile leaves, and eventually a 
terminal whorl of simple fertile leaves laterally connate 
to form a disc. Each of these produce a number of 
oval gametangia, not incrusted, opening by a lid and 
setting free a number of isoplanogametes. Germin¬ 
ation of zygotes direct. 
(b) SIPHONOCLADEAE. 
Thallus septate in the vegetative condition into segments 
containing at least two, usually many, nuclei. 
[This group consists of a progressive series of forms in which the 
strictly siphoneous type is gradually abandoned, and the thallus becomes 
partitioned into smaller and smaller compartments which contain fewer 
and fewer nuclei. On germination of the zoospore in the most primitive 
forms quite a large strictly siphoneous thallus may at first arise, in which 
a number of secondary septa simultaneously afterwards appear. In the 
higher forms the septation takes place much earlier, so that the ontogeny 
does not so clearly recall the phylogeny. In those forms that depart 
most from the siphoneous type (unbranched Cladophoraceae) the septa¬ 
tion is very abundant and the number of nuclei present in each segment 
is much reduced (sometimes to two), so that the thallus-segment 
approaches closely to the organisation of a true cell.] 
Fam. VII. Valoniaceae. 
Thallus when young truly siphoneous for a longer or shorter time, 
but always (except in Halicystis and Apjchnia) becoming partitioned when 
adult into segments containing a large number of nuclei regularly spaced in 
the parietal protoplasm. The chloroplasts are very numerous angular 
discs typically arranged in chains to form an open net work lining the 
wall. Plant attached by a branched rhizoid system (except Halicystis.) 
