OA' THE XATLRE OF CELL-ORGAXIZATJUX. 89 



Now, this morphological criterion of an organ, which 

 necessarily relates to the history and mode of its origin within 

 tJic on^wtisiii, by the dijfiTcntiatioji of its parts, does not apply 

 to the chromatophore in a green plant, nor to the "gonidia" 

 in a lichen thallus, although there can be no doubt whatever 

 that these structures serve as organs in the physiological sense, 

 in the respective organisms. The chromatophores are not 

 the products of differentiation of an homogeneous germ of 

 the plant. They can only originate b}' the division of i)re- 

 existing chromatophores, if we follow such botanists as Schmitz, 

 Schimpcr and Meyer. ^ The colorless protoplasm of the i)lant 

 and the chromatophores are the coexistent but independent 

 structures, with no genetic connection between them. 



In the organization of a lichen, the case is clearer and more 

 to the point of our inquiry. As is well known, the "gonidia" 

 and their supporting meshwork are derived from two different 

 groups of plants, I'i.z., AlgcE and Finigi, respectively, although 

 their physiological adaptation to each other is so perfect, so 

 much so, in fact, that in several lichens the hyphas of the 

 fungus cannot live when separated from the algal portion, the 

 "gonidia." Here, again, it is needless to say that these two 

 organs are not the products of differentiation from some homo- 

 geneous anlagc as different organs are in one of the complex 

 animals.^ On the other hand, the "gonidia" of one individual 

 lichen are genetically related to the "gonidia" of another, and 

 not at all to the hyphae of the thallus. In a similar way the 

 hyphae of one individual lichen are genetically related to the 

 hyphae of another lichen of the same species, and iiot to 



1 Schmitz : Dk Ctiromatophorcii dcr Ali^en, Bonn, 1882. Schimper : Ueher die 

 EnttoickcliiHg der C/ilcrophylliydnicr mid Farhiyorpcr, Bot. Zeit., 1S83, 41. Jahrg. 

 Meyer : Ueber Krystalloide der Tropltoplaslcii mid iibcr die CJirimioplastcii dcr 

 Atigtospertnen, Bot. Zeit., 1S83, 41. Jahrg. 



- Before the discovery of the true nature of lichens, it was thought that both 

 " gonidia " and supporting fungal hypha; were the products of development of a 

 single germinating spore. "Gonidia," which are the symbiotic algal cells, were 

 supposed to be, as the term indicates, ase.xual organs of reproduction produced 

 from the hyphre and capable of development into a new and perfect lichen-thallus. 

 The view that hyphae might also be produced from the "gonidia" was often 

 expressed. De Bary, Historical Ahitice of tJic LicJiens. Comp. Morphology and 

 Biology of Fungi, etc., p. 416. 



