THALLOPHYTES. 
and apex of growth can be distinguished, and a kind of branching makes its 
appearance. 
Although zoogonidia, in the sense in which the term is used in the higher 
Thallophytes, do not occur (with the exception of some Palmellaceae which perhaps 
do not belong to this class), many Protophytes are nevertheless endowed with a 
power of motion by means of which they swim about ; spirally-wound multicellular 
filaments turn on their axis; or the filaments themselves bend backwards and 
forwards; or some other kind of motion occurs. 
No sexual organs have yet been observed, and in most cases there are no 
non-sexual organs of reproduction, the multiplication of individuals being effected 
by the separation of the ordinary vegetative cells \ In other words, organs for 
nutrition and reproduction are not differentiated ; it is only in the most highly 
developed forms that cells of peculiar form are produced for the sole purpose of 
reproduction. 
The class has hitherto been divided into three groups distinguished by their 
colour; viz. i. those containing pure chlorophyll, Palmellaceae; 2. those in which 
the chlorophyll is mixed with a blue pigment, and which therefore appear of a lio-ht 
green or bluish green colour, Cyanophyceae ; and 3. those in which there is no 
chlorophyll, Schizomycetes and Yeast. While limiting the class of Protophyta 
to these three groups, it is nevertheless possible that some of the forms included 
in it are not independent species, but merely stages in the development of other 
higher Thallophytes, which have a perpetual power of reproducing themselves. 
Thus it has already been determined^ that the genus Pleurococcus, hitherto placed 
among Palmellaceae, is merely a stage of development of Chlamydomonas which 
belongs to Pandorineae, a class of Zygosporeae ; • and it is not improbable that 
the whole group of Palmellaceae, and perhaps also some Chroococcaceae, are 
of the same nature, and must at some time be eliminated from the class of 
Protophyta. 
FORMS CONTAINING CHLOROPHYLL. 
A. CvANOPHYCEiE. These organisms are of a bluish, emerald, or brownish green, 
or some similar colour, due to a mixture of true chlorophyll and phycocyanin ; this 
pigment becomes diffused out of dead or ruptured cells, and thus produces the blue 
stain on the paper on which Oscillatoriese are dried. From crushed specimens 
treated with cold water phycocyanin is extracted as a beautiful blue solution, 
blood-red in reflected light ^. When the crushed plants are treated with strong alcohol 
after the extraction of the blue pigment, a green solution is obtained which contains 
true chlorophyll, and probably a special yellow pigment, phycoxanthin*. 
I. The Chroococeaceas exist as isolated roundish cells or in roundish families, the 
cells of which are imbedded either in an amorphous mucilage or in the swollen walls 
of their mother-cells. They occur as gelatinous growths in damp places. Several 
genera are distinguished, with numerous species: — e.g. Chroococcus and Gloiocapsa 
^ [Gonidia have been discovered in Glceocapsa by Bornet (Ann. sei. nat., ser. V. XVII ; in 
Nostoc by Janczewski {ib. XIX), and in Bacillus by Cohn (Beit, zur Biol. d. Pflzn. I).] 
^ Cienkowski, Bot. Zeit. 1865, no. 3 ; and Rostafinski, Bot. Zeit. 1871, p. 786. 
^ Cohn, in Schulze's Archiv für mikrosk. Anatomie, vol. III. p. 12. — Askenasy, Bot. Zeit. 1867. 
* Millardet and Kraus, Comptes Rendus, vol. LXVI. p. 505. 
