TRANSACTIONS OF SECTION K. 585 
CAPE TOWN. 
WEDNESDAY, AUGUST 16. 
The following Papers were read :— 
1. On the more Recent Advances in our Knowledge of Seaweeds. 
By Professor R. W. Puriuies, W/.4., D.Se. 
Marine plant-life may be distinguished as attached shore vegetation or floating 
oceanic vegetation. 
I. Shore Vegetation.—With rare exceptions this consists of Aly@:—blue- 
green, green, red, and olive-brown. Gaps still exist in our knowledge of the repro- 
duction of some members in the green group, especially Siphonacee. Oltmanns 
has revised our view of the act of fertilisation in the red seaweeds. In the brown 
group, which constitute the great bulk of shore vegetation, the most interesting 
advance comes from Williams’s discovery of the existence of motile antherozoids 
in Dictyotacee. His subsequent study of the cytology of plants of this family 
points to the existence of a sharp alternation of generations. The point at which 
reduction of the chromosomes takes place in Fwcacee had been previously esta- 
blished by Farmer and Williams. There is still lacking successful cultivation 
of seaweeds ‘from spore to spore.’ The early stages of germination have been 
observed in some Phozoosporee, and exhibit points of interest. 
II. Oceanic Vegetation.—In our knowledge of the floating vegetation of the 
open sea great advance was made by the members of the German Plankton Hx- 
pedition, and later by other observers. It is enormous in aggregate amount, 
although consisting of microscopic forms taken only by the tow-net. It exists for 
the most part in the superficial 50 fathoms; below 700 fathoms is probably con- 
tinuous darkness, where no chlorophyll-containing organisms can survive. The 
adaptations in oceanic plankton to prevent rapid sinking are remarkable. It con- 
sists chiefly of Diatomacee and Peridiniacee. Coccospheres, Rhabdospheres, Ha/o- 
sphera, and Pyrocystis are also interesting forms. Upon this oceanic vegetation, 
rather than the shore vegetation, it would seem that marine animal life—large and 
small—must ultimately depend for sustenance. 
2. The Prothallium of Gleichenia pectinata, 
By Professor D, H. CAMPBELL, 
The prothallium and the reproductive organs (especially the antheridium) of 
this species show a near approach to those of Osmunda. 
3. On the Healing of Parenchymatous Tissues in Plants. 
By Professor M. C. Porter, I.A., /.L.8. 
With regard to the healing of weody tissues when exposed by a cut or other 
‘wound, Temme has shown that the cavities of the xylem vessels especially, and 
of the other elements of the wood, are closed by a substance which he termed 
wound-gum. By the development of this wound-gum, which usually takes place 
within twenty-four to forty-eight hours from the time of injury, any loss of water 
at the wound, which might interfere with the transpiration current, is checked or 
completely stopped in a very short time; and, further, the interchange between the 
atmospheric gases and those in the intercellular spaces is restored to the special 
organs for this purpose, e.g., stomata or lenticels. ‘The presence of wound-gum 
increases the specific gravity of the exposed xylem (wound-wood) and causes it to 
assume the colour and texture of the duramen ; hence Temme considers the wound- 
wood and duramen to be identical. 
The formation of callus by exposed parenchymatous cells is well known, and 
