226 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



plants of CusciUa (Peirce 1893), but no one would venture 

 to intimate that this phanerogamic parasite, containing traces 

 of chlorophyll and therefore less incapable of elaborating 

 non-nitrogenous food than any fungus, does not distinctly 

 injure every cell into which its haustorial cells penetrate. 

 In the lichen, each green cell penetrated by a haustorium 

 is obliged to manufacture non-nitrogenous food in quantity 

 sufficient to supply both the haustorium and itself, and not 

 only for the haustorium but also for the cell of which it is a 

 branch and for the cells adjacent to it. How long can a 

 green cell do this unusual amount of work ? Certainly 

 not for so long as it could do less work. The life of the 

 individual cell is therefore shortened. Overwork, exhaus- 

 tion, death, and finally the complete absorption of its con- 

 tents, follow the penetration of a haustorium. Is the 

 presence of the haustorium so beneficial or so pleasant as 

 to compensate the gonidial cell for its increased work and 

 and decreased span of life ? 



Turning once more to Cuscuta and its host for compari- 

 son, we find that both host and parasite are multicellular, 

 that owing to the division of labor among the cells one cell 

 can help another. For instance, if the photosynthetic or 

 other food-elaborating activity of a green cell is reduced by 

 the intrusion of a haustorial cell, the former will be sup- 

 plied by its neighbors, in accordance with the laws of 

 diffusion and osmosis, with those substances which it lacks. 

 This is an inevitable physical as well as a regular physio- 

 logical phenomenon, the result of the multicellular condi- 

 tion of the host. Thus the hfe of the penetrated cell, fed 

 by its neighbors, may be prolonged; the struggle between 

 host and parasite is more nearly equal, each haustorial cell 

 draws upon more than one cell of the host to supply the 

 more than one cell of the parasite. This last is also true of 

 the fungus in the lichen, for there are many gonidial cells. 

 But the gonidial cells are distinct from one another; the 

 fungus is a multicellular plant, with the advantages of one; 

 the gonidia — actually in Ramalina and in many other 

 \\c\i^vi^, virtually '\x\ all — are unicellular plants with their 



