PHAEOPHYCEAE 



245 



For the growing points and conceptacles, small pieces should be cut 

 off with a razor. If the fruiting tips be cut through lengthwise before 

 they are cut off, the fixing will be more satisfactory. For sections of the 

 conceptacles it is better not to cut across the whole tip, but to cut off 

 pieces of the rind containing half-a-dozen conceptacles. Such pieces 

 are more easily imbedded and cut. There is no difficulty in cutting such 

 pieces in paraffin. Iron-haematoxylin is a good stain. Safranin and 

 gentian violet are also satisfactory, but care must be taken not to over- 

 stain since Fiicus usually stains deeply and rapidly. 



Pjq Qi — Fi/cu.s vesiculosus: A, antheridial branch with antheridia in various stages of develop- 

 ment; 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 m. 

 stained in iron-alum haematoxylin. X480. 



For the cytologist, Fucus might be used as a test object for testing 

 proficiency in technique, just as Pleurosigma angulatimi is used in test- 

 ing an objective. The nuclear divisions in the antheridium are simul- 

 taneous, and at the sixth division, which is the last, there are 32 mi- 

 totic figures, each with 32 chromosomes which split so that 32 go to 

 each pole. When you can make a preparation in which these chromo- 

 somes can be counted, your technique is adequate for research work 

 in cytology. In a good preparation, the mitotic figures in the oogonium 

 show small but brilliant centrosomes, with a great display of radia- 

 tions (Fig. 61). 



