202 
METHODS IN PLANT HISTOLOGY 
(known as Cuileria) and the sporophyte (known as Aglaozonia) are 
so different that they furnish a good illustration of alternation of 
generations. Beginners understand such an illustration more readily 
than they do an illustration like Didyota, with its two generations 
looking so nearly alike. Cutleria also furnishes a good stage in the 
evolution of sex, about midway between isogamy and the extreme 
heterogamy of Fucus. 
Fig. 49. —Fucus vesiculosus: A, antheridial branch with antheridia in various stages of 
development; B, the third mitosis in the antheridium, one figure showing a transverse view in 
which the chromosomes can be counted; C, the fourth mitosis, with two of the eight figures cut 
transversely but hard to count chromosomes in the figure, which is reduced one-half; D, the 
third mitosis in the oogonium, showing centrosomes and radiations. Fixed in Flemming’s weaker 
solution, cut 3/x, stained in iron-alum haematoxylin. X480. 
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, fix in chromo-acetic acid. Cut 10 y thick. 
For mitotic figures, some osmic acid should be added to the chromo- 
acetic acid and the sections should be much thinner, about 3 to 5 /x- 
Use iron-haematoxylin and then stain for 3 to 5 minutes in alcoholic 
safranin (Fig. 48). 
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 
