378 Spratt. — Some Observations on the 
capable of obtaining its energy from the sun and manufacturing carbo- 
hydrate food material, not only for its own wants, but also sufficient to 
supply the source of energy to the Bacteria, which in their turn supply 
the nitrogenous material available to the Alga ; and all three find a habitat 
in the Gymnospermous plant, which undoubtedly benefits in its turn from 
the products of the metabolic activities of these organisms. 
In conclusion, my most sincere thanks and gratitude are due to 
Professor W. B. Bottomley for his kindness and advice during the progress 
of the work, and to Dr. Fritsch for many helpful suggestions. 
Summary. 
1. Anabaena Cycadeae is a typical Anabaena. 
2. Each mature cell has two investments, an inner and outer, in addition 
to the external mucilaginous sheath. 
3. The chlorophyll and phycocyanin are lodged in the peripheral 
cytoplasm, no definitely organized chromatophore being present. 
4. The central body is a simple structure only capable of direct 
division. 
5. The chief product of assimilation is glycogen. 
6. Cyanophycin granules are very abundant. 
7. In the vegetative division the ingrowth of the lateral walls is accom- 
panied by direct division. 
8. Terminal and intercalary heterocysts are formed from vegetative 
cells. They may become detached, and appear to have three functions : — - 
a. To limit the filaments — vegetative reproduction. 
b. For storage of reserve food material. 
c. Reproduction by formation of gonidia. 
9. Spores are formed. The exospore and endospore are the fully 
developed cell sheath and inner investment respectively. 
10. There are four types of spore germination : — 
a. The contents are protruded through a pore in the spore 
membrane. 
b. The spore membrane is ruptured. 
c. The spore membrane becomes mucilaginous. 
d. The contents divide before escaping from the spore wall. 
11. Gonidia are formed by the rejuvenescence and subsequent division 
of the contents of the heterocysts. A distinct membrane appears inside the 
walls of the heterocyst. A number of spherical gonidia are formed, each 
of which is capable of dividing to form a new Anabaena filament. 
12. Anabaena Cycadeae maintains its existence in the soil in the form 
of heterocysts and spores, which develop into gonidia, and these enter the 
Cycas tubercles through the lenticels. 
