268 PROCEEDINGS OF THE AMERICAN ACADEMY. 



It has been the view of some writers that the joeridium is the result 

 of a development from a circle of paraphyses, and the condition of the 

 SBcidium of Phragmidium is cited in support of this view. But, as 

 De Bary * has said, the paraphysal envelope of this secidium is not 

 well understood, and no light has been thrown on this matter since 

 he wrote regarding it. Whatever may be the condition in this 

 a^cidium, however, it is safe to say that the peridium of the ordinary 

 aecidium is the result of a metamorphosis of the outer layer of spores. 



As to what interpretation is to be placed upon the lecidium, and 

 what place it occupies in the life history of the Uredineoe, so much has 

 been said, and so little comparatively is known, that a re-discussion 

 cannot bring out much that is new. What has been described in this 

 paper, although perhaps not of the most positive nature, certainly 

 rather suj^ports than contradicts the view held by De Bary. In the 

 secidia here investigated, it would seem that the aecidium is not to be 

 regarded at the present time as the result of a sexual process, but that 

 it has a definite spore-bearing hypha, possibly corresponding to the 

 arch i carp. 



Some of the more recent writers in text-books have entirely disre- 

 garded De Bary's view, and speak of the Uredineai as forms of 

 fungi with three chlamydosporic stages, in some cases comparing the 

 chains of a;cidiospores and their interstitial cells with the chlamydo- 

 spores found in Chlamydomucor. This seems to carry it to some- 

 what of an extreme, for one certaiidy does not associate with 

 chlamydosporic conditions such relatively complicated sporocarps as 

 are found in the Urediuete. 



Vuillemin f has recently published an account of the a?cidiospores, 

 in which he maintains to have found the equivalent of a sexual stage 

 in the union of the double nuclei found in these spores. The question 

 of the sexuality of such a process, should it occur, ran hardly be dis- 

 cussed here, for the idea itself naturally suggests its own objections, 

 particularly in the light of the ubiquity of the double nuclei through- 

 out the Uredinete. It is interesting to note in this connection a fact 

 already recorded, that triple nuclei have been not infrequently seen. 



To sum the whole question up, it seems to the writer that the view 

 expressed on this question by De Bary, where he likens the iEcidium 

 to the sporocarp, has more basis in fact than any other theory, but that 

 at the present time there is no sexuality in the process of the forma- 



* Loc. cit., p. 246. 



t Comptes Rendus, 1893, Vol. CXVI. p. 1464. 



