RKAiTIoN OF HOST TO PARASITIC ATTACK. 



effect "(' haustoria of Uredineae on the cell-nucleus. He describes 

 it thu- : 'The mycelium of Pm-i-in'm <wirina permeates between 

 the culls of the leaf-tissue of Asarum, and sends into almost 

 every cell of the infected part, a short, sometimes branched, 

 livpha. which serves as a haustorium. This grows in almost 

 every case towards the nucleus of the host-cell, and becomes 

 firmly attached thereto, or completely encloses it. The nucleus, 

 in consequence, undergoes considerable deformation, sometimes 

 beiii'j; tightly constricted by the haustorium, or the apex of 

 the hyplia penetrates deep into the nucleus, pushing the nuclear 

 membrane before it." 



Kiil.ir-einriit of the cell-nucleus occurs, according to Frank, 

 in the cells of the root-tubercles of Legumiiiosae caused by 

 bacteria; likewise in the cells of endotrophic mycorhiza of 

 orchids. Schlicht, 1 in considering the endotrophic mycorhiza of 

 J'ni-i* ijiKnli-ifolia, says, "One observes here, as in the mycorhiza 

 of the Orchideae, that the cell-nucleus, which is very large, can 

 exist in the cell beside the fungus-tissue. The hyphae, however, 

 frequently penetrate into the cell-nucleus, or surround it in 

 a close network." 



The effect of parasitic fungi on the chlorophyll of tissues 

 attacked by them is very varied. We may distinguish three 

 cases, apart from those in which the parasite kills the host-cell 

 and its chlorophyll along with it. In the first, the green parts 

 of the plant attacked become bleached by the influence of the 

 parasite, and ultimately lose their green colour ; this we might 

 designate <: mycetogenous chlorosis." Examples are the galls 

 of cowberry and species of rhododendron, the results of many 

 Uredineae, such as Chrysomyxa rlwdodendri on spruce, Accidin/n 

 urticat' on nettle, Crymnosporangium clavariaeforme on hawthorn, 

 and the leaf-galls due to Exoasceae. 



In the second case, there is a preservation of the chlorophyll 

 in places infested by the fungus, in contrast to adjoining normal 



Si hlirht. "Beitragez. Kenntniss d. Verbreitung u. Bedentune d. Mycorhizen. " 

 Inaug. Diss. 1889, p. 14. 



(" Thiamia Aseroe and its Mycorhiza," Annals of Botany, June, 

 1S<.~>, ]>. 339) describes and figures a similar case. He says, "The fungus 

 enters the cell as a single slender hypha, which at once grows directly towards 

 the imrlriis of the host-cell." He also mentions an observation of Professor 



Marsli;ill Ward, "that in Hi-tni'< in of the coffee disease, the haustoria often apply 

 thi-iii-> ] > - to the nuclei of the host's cells." (Edit.). 



