OF ARTS AND SCIENCES. 49 



large, somewhat irrefrnlar cells, approaching a spherical or cylindrical 

 shape, which are lilled with coarsely grauular, almost colorless con- 

 tents. The cells are separated, except at narrow points of contact, hy 

 an almost structureless gelatinous intercellular substance (Fig. 8), 

 This gelatinous substance, which contains a large amount of water, is 

 found to a greater or less extent between all the cells of the frond, and 

 gives to it tlie consistency already mentioned. The large cells which 

 make up the interior of the frond are not at all regular in either size 

 or slm()e, some departing so far from the spherical as to become al- 

 most branched, by the excessive growth of some portion of the cell in 

 some other direction than that of the main axis. Tiiey are not ar- 

 ranged in filaments, or in any distinct order, but are joined in a loose 

 parenchymatous network. In the parts of the frond near its point of 

 attachment to the host plant, the cells are seen to be smaller and of a 

 different sha[)e than those of the rest of the plant. They are cylindri- 

 cal, with one axis considerably longer than the others, and are arranged 

 in filaments of greater or less length (Figs. 8, 14). The filaments 

 which may or may not branch, make their way beneath the peripheral 

 siphons of tiie Polysiphonia, encircling its axial row of cells. Usually 

 these filaments extend from the frond of Choreocolax fi'om which they 

 arise, through the length of three or four cells ; cases were observed, 

 however, where they had penetrated as many as ten cells from their 

 starting point. It is by means of these cells that the Choreocolax ob- 

 tains elaborated material from the Polysiphonia, on which it depends, 

 in a large measure at least, for its nourishment. The close connec- 

 tion which the filamentous cells of the parasite have with the cells of 

 the host may be easily demonstrated. A section shrunk in glycerine 

 and stained with Ilofraann's blue, enables one to see with the greatest 

 distinctness threads of protoplasm connecting the cells of the two 

 plants (Fig. 7). Material killed in osmic acid also shows this point 

 to advantage. At the same time it will be seen that the cells of the 

 Choreocolax attach themselves almost wholly to the cells of the central 

 siphon, although sometimes the walls of the peripheral siphon are 

 penetrated and the material afforded by them appropriated by the 

 parasite. C. PoJysiphonicB is then, as Reinsch first maintained, a true 

 vegetable parasite, which depends in the main for its nourishment on 

 the materials provided by its host, exerting upon the latter nothing 

 but a deleterious influence. These filaments were never seen to 

 connect with any of the external swellings except the one from 

 which they arose. Each swelling then represents a separate frond, 

 and there is no continuous growth of filaments which ramify through 

 VOL. XXVI. (n. s. xviii ) 4 



