2472 



Journal of Applied Microscopy 



a dish of water so that the above mentioned process may be studied. If this 

 stage is at hand draw and describe carefully. 



8. Write out the life cycle of this plant in the notes, giving the stages in 

 proper order and noting that the plant has two definite stages in its history — 

 the gametophyte and the sporophyte. 



XLII. Oedogo/iiiim borisianum (LeCl.) Wittr. 



This species grows in stagnant brooks or in ponds and ditches, usually 

 attached to solid objects. The plants are coarse unbranched filaments and they 

 may be grown in an aquarium. 



1. Mount in water and study under low power. Note the long unbranched 

 filament and the basal cell expanded into a holdfast. Under high power draw 

 the tip of a filament, several intermediate cells, and the holdfast. At the summit 

 of certain cells broad zones with peculiar ring-like striations may be seen. This 

 is where cell division has taken place. Draw. 



2. Draw a single cell, showing the chloroplast with pyrenoids and the nucleus. 



Fig. 6. — Diagram of life cycle of Coleochjete. 



3. Study vegetative cells in which zoospores are developing. These can 

 be seen especially in the morning or in material which has been chilled over 

 night. Draw a single, large zoospore with a circle of short flagella or cilia 

 around the hyaline anterior end. 



4. Draw part of a filament, showing oogonia, some with an oosphere and 

 an opening in the wall for the entrance of the spermatozoid, and others with 

 thickwalled oospores. 



5. Draw some of the so-called andro-sporangia, which consist of two to five 

 short cells. These cells give rise to zoospores known as androspores, which 

 settle down on the cells below the oogonia and develop into dwarf male plants. 



6. Draw part of a filament with oogonia and one or more dwarf males. 

 Note the large basal cell of the dwarf male and the more slender antheridium 

 composed of a number of cells. 



7. When the oospore germinates after a period of rest the cell breaks out 



