BoT.-VoL. II.] HUS—PORPHYRA. 233 



added. After this they were transferred to absolute alcohol, 

 xylol, and finally mounted in Canada Balsam. On examin- 

 ation the slides showed that while the cushion-shaped base 

 of P. iiaiadum stained a bright red, the tissue of the host- 

 plant, Phyllospadix, was stained blue, as were the chromat- 

 ophores and cell-contents of P. naiadwn. In some cases, 

 where the slides had remained longer than five minutes in 

 the methyl-blue, the young fronds emerging from the 

 cushion-shaped bases were stained purple. 



The ribbon was fixed on the slides with albumen, and 

 floated out in water and placed on the top of the water-bath 

 where the slides remained till dry. 



As regards mounting media, dilute glycerin jelly and 

 Farrants' Medium gave excellent results. While the 

 former can be used to great advantage in preparing 

 surface views, the latter is to be preferred where razor 

 sections are to be mounted. It appears to have a clearing 

 action on the tissues. Great care must be taken to wash out 

 all corrosive sublimate in alcohol to which some potassium 

 iodide is added, while hardening preparatory to cutting, 

 since even the slightest trace of mercuric chloride will 

 after a time attack the mounting medium and destroy the 

 preparation. 



In conclusion, the author begs to acknowledge his in- 

 debtedness to Professor W. A. Setchell, at whose sugges- 

 tion the work was undertaken, and whose advice has been 

 of invaluable aid in compiling this paper. Thanks are also 

 due Professors Rosenvinge, Kjellman and Farlow, Messrs. 

 Bornet, Collins, Janczewski, de A. Saunders, Lawson, 

 Gibbs and Nott, and Mrs. Weeks and Mrs. Snyder, for 

 specimens received. 



Botanical Laboratory, 



University of California, 



Berkeley, California. 



