28 KKA< TloN i)F HOST TO PARASITIC ATTACK. 



inav also be seen amongst lower cryptogamic plants, two cases 

 of which may lie mentioned here. 1 Plcotrachdus fulyens, 

 inhabiting the mycelium of Pilobolus Kleinii, causes the 

 I'urmatiun of galls and the suppression of sporangia, while at 

 tin' same time xygospores, normally rare, occur in large 

 numbers. Likewise a species of ^///in-jthalis parasitic in Pilubolus 

 r,-i/xhi1l<i<iix causes suppression of sporangia and stimulates 

 formation of xygospores. 



The transformation of floral organs may resemble that observed 

 by Ik- I'.ary, in which, as a result of attack of Peronospora 

 rinlni'iii on Kninttitt nrvcnsis, the stamens appeared in the form 

 of violet petals. Doubling of flowers is also caused, as in 

 Xn/Hi/itirit* <>j/iri/ttdis, under the influence of Ustilago saponariae, 

 and Compositae with Peronospora radii. 



The Ustilagineae, perhaps, cause the greatest amount of varia- 

 tion on the flower, because many of them produce their spores 

 in the floral organs of their host. Thus, in the anthers live 

 Uxtilayo violacea, Jwlostci, scabiosae, intermedia, succisac, bctonicac, 

 major, scorzonerae, eapensis, pinguicolae, Vaillantii, and Tubwcinia 

 jn-i/ii/'/ti'ii//(; the last named also occurs in ovaries and stigma. 

 So also do many others inhabit the ovary or some other part. 

 .Many, like Ustilnyo imn/dis, form spores throughout the plant 

 as well as in the flower, and bring about hypertrophy and 

 destruction of parts. Amongst these are Ustilago arenac, 

 l rrnnans, hordei, nuda, tritici, pcmici miliacei, reiliana, cru.cnta, 

 xi>/-i//i/, Cramcri, caricis, tragopogonis, Tillctia lacms, etc. 



Cystopus (Fig. 35) causes very characteristic hypertrophy 

 of all parts of the flower, particularly an enormous outgrowth 

 of the ovaries and floral envelopes, whereas other parts are 

 anv.sted iii their growth. Wakker investigated a number of 

 Cruciferae with flowers deformed by this parasite, and found 

 variations in the form and anatomy of the deformations 

 produced on the different host-species. 



K.i-iJxisidium also causes well-marked hypertrophy of flowers, 

 and even of the whole inflorescence of cowberry. Woronin 2 

 d.-;-ribes and figures such cases (Fig. 256). All parts of 

 the flower may be attacked and grow to a great size, becoming 



Xnpf., Beitrage zur Physiol. und Morph. niederer Oryanismen , 1892. 

 X<.|>f., "x.ur Kenntniss d. Infections-Krankheiteu nied. Thiere u. Pflanzen." 

 Nova Ann d. k. Leop. -Carol. D. Akad. Hallt., 1888, p. 356. 

 N itmforsch. Gesellschaft Freiburg-i.-B., 1867. 



