282 DR. LILY BATTEN ON 
Growth takes place by two methods of cell formation—division from the 
apical cell and * gemmation " from the axial cells. 
The form of the attachment organ varies with the species, and is influenced 
by the nature of the substratum. Four types may be distinguished :— 
l. The ecorticate plant is originally attached by rhizoids, which are 
developed from siphons by longitudinal proliferation. Later, siphons of 
procumbent branches also develop rhizoids. | Rhizoids may have disces at their 
distal ends when they encounter a hard substratum, or may ramify among 
filamentous algæ without expanding, or may be swollen to form haustoria in 
certain species. 
2. Species having a number of siphons or a beginning of cortication at the 
base show elementary aggregation of the rhizoids to form a large dise, the 
expanded tips of the rhizoids themselves interlocking mechanically. Pro- 
cumbent branches also develop rhizoids which give additional strength, and 
the cells as well as the siphons aid in the formation of the attachment organ. 
3. P. fruticulosa, which is originally attached by a number of longitudinally 
developed rhizoids, and, later, certain procumbent branches which are stunted 
function specially in the formation of the attachment organ. 
4. Species with an upright habit, which do not branch near the base, 
develop a large disc-like expansion at the base of the thallus. Such forms 
are always corticate. The siphons and corticating cells at the base all 
grow downwards longitudinally and form rhizoids. The rhizoids cuhere 
mechanically with each other, so that a pseudo-tissue is formed. 
Sexual and asexual organs of reproduetion are present in the group. 
Tetraspores are either intercalary or are borne terminally. The tetrasporan- 
gium originates in the same way as the pericentral siphons, subsequently 
dividing into two, the upper of which develops four tetraspores. 
Antheridia are borne at the tips of the branches and ramuli, each 
antheridium either replacing a filamentous hair or one arm of a dichotomous 
hair. 
Cystocarps are borne on the branches and ramuli. They are urn-shaped, 
with an ostiole at the top, which is occasionally sinuous and through which 
the carpospores are discharged. 
A classification and description of the individual species follows, together 
with a key for identification. 
ENUMERATION AND CLASSIFICATION OF SPECIES OF POLYSIPHONIA 
ACCORDING TO THEIR ANATOMICAL DIFFERENTIATION. 
I. Ecorticate Species. 
A. Four primary pericentral siphons. 
1. P. insidiosa. 4. P. spiralis. 
2. P. macrocarpa. 9. P. urceolata. 
3. P. rhunensis. 
