286 ~~ Structural and Physiological Bo 
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bluish-green colour, caused by the mixture of the colouring matterof = 
chlorophyll with a blue and yellow pigment. The form of the inst eY is 
dividual cells is discoid or nearly spherical. But little is known of ied 
their mode of reproduction. . Piha gs 
The HypDRODICTYE contain pure chlorophyll, and are distin- : 
guished by producing a large number of swarmspores which, after 
coming to rest, unite into a family. This is of tabular form in Pedias- 
trum (Fig. 58, p. 37) 3 in Hydrodictyon a sack-like wide-meshed net. 
The VOLVOCINE form colonies which are quadrangular in 
Gonium, spherical in Volvox [and Stephanosphera], the cells being im- 
bedded in a hyaline jelly. The whole colony is carried in a circular 
and progressive movement by the vibratile motion of the cilia which — 
project from the separate individuals through the jelly into the water.’ 
The CoNJUGAT are distinguished from all other Algz by their 
reproduction by the process of Conjugation. In the Zygnemez and. 
Mesocarpes the conjugation takes place between cells belonging to 
different unbranched filaments (Fig. 54, p. 32); in the Desmidiez 
(Fig. 383, p. 251) between isolated cells. [The resting-spore resulting 
from the conjugation is called a zygospore.| The Diatomacez (Bacil- 
larieze) are nearly allied to the Desmidiez. Their cell-wall is trans- 
formed into a siliceous coating, often showing markings of the most 
. beautiful delicacy (Fig. 38, p. 22, and 
381, p. 249); and the two halves fit 
into one another like the halves 
of a pasteboard box. ‘They are pro- 
i pagated by repeated bipartition: but 
=3  \S' the diameter of the successive genera- — 
ee 
SS, 5 Ge tions gradually diminishes until at 
SN = length it attains a minimum. This 
= S_F - ess is then intcrrupted Eee 
aa =~ Process is then interrupted by the form 
AA SS ation of larger cells or auxospores, and 
\ individuals are produced which reach 
the maximum size of the species, but 
Fic. 388.—Gomphonema hyalinum, a in other respects exactly resemble their _ a 
social Diatom, attached to a thread parent-cells. In these the process of vs 
of a Conferva (greatly scene): | bipartition is then again oun ein 
- 
1 [ Protococcus is a genus of Unicellular Algze but imperfectly known, 
and generally referred to this family. The species consist of single ay 
swarmspore-like bodies with a more or less evident gelatinous envelope 6 ea ds 
cellulose, through which protrude two vibratile cilia. They move’ — 43 
actively, and are multiplied by division during the active state, finally 
settling down into a resting-state. See also p. 261,.—-EpD.] ~ ;) 
