Sexual Reproduction in spirogyra is?

Answer:b
               Hints & Solutions.

• Spirogyra is autotrophic, unbranched filamentous algae which is slippery due to mucilagenous covering (pectin)  
• Cytoplasm is peripheral due to central vacuoles so called primordial utricle. 

• Sexual reproduction in spirogyra is isogamous occurs by conjugation i.e. Morphologically isogamous but physiologically anisogamous.
• Conjugation is of two types: Scalariform & Lateral conjugation. 
• Father of algae: Fritsch
• Term algae was given by: Linnaeus
• Study of algae : phycology/ algology. 
• Embryo is absent in Thallophytes. 
• Pyrenoids are found in Chloroplast. 
• Algae parasitic on tea plant is Cephaleuros. 
• Production of cap cell during respiration is seen in Oedogonium. 
• Heterocysts are commonly found in BGA. 
• Largest algae is Macrocystic. 
• Outer wall of spirogyra is made of pectic. 
• Children of sea are Algae. 
• Pyrenoids are centre of storage of starch. 
• Most primitive algae is Red algae. 
• Water bloom is caused by BGA. 
• Motile reproductive bodies are absent in Rhodophyceae.