244 



METHODS IN PLANT HISTOLOGY 



is abundant at Naples. The habits of gametophyte (known as Cut- 

 leria) and the sporophyte (known as Aglaozonia) are so different that 

 they furnish a good illustration of alternation of generations. Begin- 

 ners understand such an illustration more readily than they do an 

 illustration like Dichjota, with its two generations looking so nearly 

 alike. Cutleria, with its large, motile eggs, furnishes a good stage in 

 the evolution of sex, about midway between isogamy and the extreme 

 heterogamy of Fucus (Fig. 60). 



For habit study, both generations should be mounted upon paper. 

 The gametophyte {Cutleria) sticks well, but the sporophyte {Agla- 

 ozonia) will need some glue 

 or gummed paper. 



For paraffin sections, use 

 the Chicago formula and 

 cut 10 M thick. For mitotic 

 figures, cut 2 or 3 /z thick 

 and stain in iron-alum hae- 

 matoxylin. This stain will 

 also differentiate the cilia- 

 producing organ, which is 

 a modified portion of a 

 plastid. 



Fucus. — Material for 

 habit study may be dried, 

 or preserved in formalin, or 

 mounted on paper. In the 

 latter case, glue or gummed 

 paper will be necessary. Most satisfactory of all is to send to Woods 

 Hole, Massachusetts (George M. Gray), for living material. FertiHza- 

 tion occurs at all seasons, but autumn is the most favorable. In sum- 

 mer the material dies before it reaches Chicago, but during the rest of 

 the year a pailful will reach Chicago, and even as far west as the 

 Mississippi River, in good condition for showing the rotation of the egg 

 by the sperms. The eggs and sperms form slimy masses, the antheridia 

 being orange red and that containing the eggs, a dirty green. Mix a 

 drop of the red with a drop of the green. The movements of the egg 

 can be observed, and material for a study of fertilization and later 

 stages is easily secured. In fixing fertilization and preceding stages, 

 Flemming's weaker solution is good. 



Fig. 60. — Cutleria multifi da: A, oogonia; B, antheridia. 

 Fixed in Flemming's weaker solution, cut 3 m. and stained 

 in iron-alum haematoxylin. X470. 



