36 



PLANT MORPHOLOGY 



Protosiphon. Protosiphon is a unicellular coenocytic alga occurring 

 on damp earth. It shows a striking resemblance to Botrydium, one of 

 the Xanthophyceae, and often grows with it in the same habitat. The 

 plant has a green aerial portion that is tubular or bladder-like and a 



Fig. 25. Hydrodictyon reUcnlaium. A, portion of colony, X 150; B, single cell with many 

 nuclei and pyrenoids, X350; C, young net formed within a parent cell; D, a gamete; E, 

 gametes fusing; F, zygote; G, four zoospores escaping from zygote; H, a zoospore escaped 

 from zygote; /, polyhedron formed by a zoospore; /, young net escaping from polyhedron. 

 (C to F, after Klebs; G to J, after Pringsheim.) 



colorless underground portion that resembles a rhizoid (Fig. 26A). 

 It is entirely without cross walls. The cytoplasm, in a thin layer sur- 

 rounding a large central vacuole, contains numerous scattered nuclei 

 (Fig. 26B). When young, the cell has a large reticulate chloroplast 



