210 Mr John Eattray on some 



members of the family in question, it is not unlikely that 

 a more intimate parasitic connection exists between several 

 ibrms. In the former case the minute filiform rhizoids of 

 the epiphyte simply twine round any part of the thalli, or 

 round the ramuli, of the host plants, and grasj) these 

 exclusively for the purpose of securing support, as they 

 might lay hold of any other foreign body of corresponding 

 size in suitable localities, but they in no sense derive 

 nourishment more simply as a result of the act ; whereas, 

 in the latter case, the rhizoids come into the most intimate 

 connection with the cells of the host plants, and extract 

 from them some of the highly elaborated organic matter 

 that is passing through their simple tissues. Thus in those 

 algse that are found on many different hosts,, and that may 

 accordingly be looked upon as exhibiting but few selective 

 properties — such as Ceramium rubrum (Huds.) Ag., C. 

 diaplianum (Lightf.), Roth., C. DesloiKjcliampsii^ Chauv., 

 Gallithamnion Hookeri, Ag., 0. 2Joli/spermum, Ag., CladO' 

 phora Icetevirens, Kiitz., Delesseria alata (Huds.), Lamour, 

 D. sinuosa (Good, et Woodw.) Lamour, Ectocarpus sili- 

 culosus, Kiitz., E. littoralis^ Lyngb., Enteromorpha com- 

 pi'essa, Grev., Plocamium coccineum, (Huds.), Lyngb., 

 Porpliyra lacinata (Lightf.), Ag., Ptilota plumosa (L.), 

 Ag., JJlothrix flacca (Dillw.), Thur., 31onostroma latissima 

 (Kiitz.), Wittr., and others — it is not unfrequently possible, 

 by careful manipulation under a dissecting microscope, to 

 unravel the rhizoidal plexus, so as to exhibit its separate 

 parts in an intact condition. In this manner the effects 

 produced by the epiphytes upon the host plants as a whole, 

 and upon their individual parts, become manifest. Among 

 these may be noted the following : — 



1. Slight local modifications of the external cell mem- 

 branes immediately around the areas affected. These 

 modifications assume the character of very delicate and in 

 many instances hardly appreciable swellings. 



2. Alterations in the appearance, and consequently in the 

 physiological activity, of the endochromaceous granules that 

 are located just beneath the areas that are grasped. These 

 changes are sometimes manifested by delicate modifications 

 in the hue of the granules ; those, for example, of Chloro- 

 spermic hosts, being somewhat paler than in adjoining 



