210 



THE AMEBIC AN NATURALIST [Vol. XLIV 



nervis, it reacts with much greater pigment production; 

 a reaction which shows itself with great defmiteness in 

 the buds and the rosette leaves. 



Although plants and animals equally exhibit Mendelian 

 phenomena, yet the part of the organism which must be 

 looked upon as constituting the germ plasm, and hence 

 the basis of such phenomena, shows several important 

 differences in Metazoa and Metaphyta, two of which may 

 be pointed out. Most important of these differences is 

 probably the absence of a Keimbahn in plants, in the 

 sense in which it is known to be present in many animals. 

 The classical cases of Ascaris (Boveri) and Cyclops 

 (Hacker) need only be cited. More recently, other work, 

 such as that of Hegner ( '09) in the Coleoptera, has shown 

 that the germ cells are formed from certain free nuclei, at 

 an early stage in the segmentation of the egg. Thus set 

 aside, they rest and undergo very few divisions, until 

 a late stage of embryonic life. There is no evidence 

 whatever of a similar process in higher plants, and it is 

 probably made impossible by the method of plant growth. 

 On the other hand, it may be pointed out that while, in 

 plants, there are no resting cells set aside in the body 

 tissues, to serve later as reproductive cells, yet a lineage 

 of cells exists, which may be looked upon as a Keimbahn 

 in one sense. Every one who lias studied plant embryos 

 recognizes their characteristically large nuclei with huge 

 nucleoli having a large chromatin content. A similar 

 appearance is characteristic of all undifferentiated 

 meristematic cells, so that such cells, forming a lineage 

 from the egg cell to the spore mother cells, may be 

 thought of as constituting a Keimbahn for the plant, 

 though evidently in a somewhat different sense from 

 that in which the term is employed for animals. The 

 fact that in such a lineage, a great number of cell genera- 

 tions intervene between the fertilized egg and the spore 

 mother cell, together with the fact,that the meristematic 

 cells forming this lineage are near the surface of the 

 plant, where they are almost directly exposed to en- 

 vironmental influences (and not hidden away in the in- 



