96 TYPE STUDIES 



Questions. How would you distinguish aquatic species of 

 Vaucheria in the field from Spirog[/ra ? from (Edogonium ? 

 Describe the protoplasmic structure of the filaments. What 

 are the characteristics of a coenocyte ? Do the nuclei occupy 

 fixed positions in the filament ? Where in the filam^ent does 

 growth in length take place ? Compare the structure of the 

 ccenocytic zoospore of Vaucheria with the protoplasmic 

 contents of a sporangium of such a tj^pe as Cladophora (see 

 Princijdes, Fig. 184, B) or the water molds (see Principles, 

 Fig. 214, C) and show the points of resemblance. What 

 difference in the behavior of the protoplasm results in the 

 formation of a single zoospore in Vaucheria and of many 

 zoospores in the other forms? What takes the place of 

 starch in Vaucheria ? Would the oospore from its structure 

 be expected to germinate at once ? Describe the life history 

 of Vaucheria. 



91. Chara or Nitella, stoneworts. Examine the growth habits of the plant. 

 Is the surface incrusted with lime ? Study the general morphology, noting 

 the well-defined stems, the circles of lateral, leaf -like hranchlets, the joints or 

 nodes separated by internodes, the growth from a bud-like tij). Are these 

 characters which would be expected of a thallophyte ? Is the structure a 

 thallus ? Sketch these features of the general morphology. 



A. In fruiting material, either living or preserved, note the position of 

 the sexual organs, generally in pairs, an antheridium and an oogonium. 

 If the antheridium is above the oogonium, the form is Nitella; if 

 below, Chara. Material heavily incrusted with lime may be treated 

 with 1 per cent chrom-acetic acid, which will dissolve it away. Draw 

 a group of sexual organs, shoAving : 



1. For the oogonium, the circle of five spirally \no\x\\(\. filaments, adher- 

 ing to one another side by side, which envelop the egg, the tips of 

 the filaments projecting beyond the es:g as the crown. If there 

 are five cells in the crown, the form is Chara; if two tiers of five 

 cells each, the form is Nitella. 



2. For the antheridium the surface view of large, triangular, flattened 

 cells, called shields (eight in all), composing the outer envelope. 



B. Crush the antheridium, noting the numerous coiled antheridial fila- 

 ments, composed of disk-shaped cells, each of which develops a sperm. 

 The attachment of the antheridial filaments by means of a series of 



