252 ROMANCE OF LOW LIFE AMONGST PLANTS. 



supplied in the preceding chapter on the " Trimor- 

 phism of Uredines." It will be seen that, in the 

 example given, all the phases were passed upon a 

 single species of host plant, and, whatever form the 

 uredine assumed, that form was developed upon 

 the leaves of the " Nipple-wort." Bearing in mind 

 the fact that the consecutive ^ciduim, Uredo, and 

 Piiccinia are accepted as three manifestations of the 

 same parasite in different stages or forms, the problem 

 which presented itself for solution was to harmonize 

 with this conclusion the two anomalies, that certain 

 forms of ^cidiiini are constantly being produced 

 upon berberry leaves, coltsfoot, and other plants, 

 with no corresponding Uredo or Piiccinia ; and that 

 also certain forms of Uredo and Piiccinia are habitu- 

 ally developed upon grasses, sedges, and other allied 

 plants, which never produce an Aicidiuin. In order 

 to reconcile these anomalies, the hypothesis of 

 " Hetercecism " has been propounded, which primarily 

 assumes the possibility that the y^cidium may be 

 produced on the leaves of one plant, as, for instance, 

 the berberry, and the corresponding Uredo and Piic- 

 cinia on another, and entirely different plant, to wit, 

 upon the leaves and culms of cereals and grasses. 

 Now, it is quite clear that an acceptance of trimor- 

 phism, as applied to a single-host plant, cannot 

 necessarily involve the acceptance of the theory, that 

 certain of the stages may be passed on one plant, and 

 the remainder upon another, and very different one. 

 Supposing the latter to be true, it must be based 

 upon direct, and not circumstantial, evidence, and 

 the hypothesis must be shown to be sufficient to 



