Phaeophyceae 



183 



whole tufts are imbedded, the branches diverge enough to make 

 perfectly longitudinal sections of the apical cells rather rare. Iron- 

 haematoxylin with a faint staining in orange is a satisfactory com- 

 bination. 



Ectocarpus. For general morphological study, branches should 

 be mounted whole in Venetian turpentine. A 6 to 10 per cent 

 formalin solution (in sea-water, of course), or the chromo-acetic acid 

 will give good fixation. Stain some in iron-haematoxylin and some 

 in Magdala red and anilin blue. Mount on each slide some from 

 each lot. Unilocular sporangia usually ap- 

 pear earlier than the pleurilocular game- 

 tangia. So collections should be made at 

 different seasons. You should have both 

 sporangia and gametangia on each slide 

 (Fig. 42). 



Desmotrichum. Forms as large as Des- 

 motrichum can be handled like Ectocarpus, 

 but care must be taken not to overstain. 



Laminaria. In such large forms, small 

 portions showing the structure and develop- 

 ment of the thallus and also the reproduc- 

 tion should be cut out with a razor and 

 then placed in the fixing agent. The 

 " sporangia" of Laminaria stain very deeply 

 and quickly. Iron-haematoxylin is good, 

 but be careful not to 



FIG. 42. Ectocarpus: from 

 a preparation stained in 



OVerstain. After Mayer's haem-alum; g, game- 

 , i ... i j v o H e tangiuna; s, sporangium. 



this stain is just right, about 3 to 5 minutes X2 * 5 

 in alcoholic safranin will stain the muci- 

 laginous structures and add to the value of the preparation. 



For habit study, small specimens up to 45 cm. in length can be 

 mounted upon paper. They stick well and seldom need to be secured 

 by gummed paper. Larger specimens may be allowed to dry and 

 may then be stored away in a box. When wanted for use, wet them 

 under the tap, or, better, in salt water; after using, let them dry and 

 return them to the box. Specimens will stand four or five such 

 soakings in fresh water; if a pint of salt is added to three or four 



