72 J. W. REED ON UROMYCES PISI. 



width. Up to the present, their function is not known ; but it is 

 difficult to believe that they have none, unless indeed they are 

 merely a survival of structures which were useful under con- 

 ditions that have long since passed away. This is probably true 

 in most instances, but sperm atia of some species have been 

 caused to germinate and produce a mycelium like that of the 

 uredo condition of the fungus. 



Sometimes the spermogonia occur in conjunction with the 

 uredospores, and sometimes in conjunction with the teleutospores, 

 though this latter is apparently not the case in the genus 

 Uromyces. 



The secidiospores are produced in basipetal chains, the oldest 

 spores being at the apex of the chain, the youngest at the base : 

 they are from 17 to 20 fx (say the ^.} -q of an inch) in diameter. 

 As the terminal spores mature they become free and form an 

 orange powder, which fills the whitish-edged and slightly fringed 

 cluster-cup. They are, at maturity, globular or polygonal, and 

 roughened on the outer surface. The walls are thinner in 

 certain places, and it is through these so-called germ-pores — and 

 as a rule from only one — that the germ-tube issues. It is these 

 germ-tubes which, finding their way through the stomata of the 

 host-leaf, start densely woven mycelial growths in the inter- 

 cellular spaces of its tissue. The mycelial tubes not infrequently 

 develop tubular suckers, called Haustoria, which penetrate the 

 cells themselves, abstracting their manufactured food-stuff's for 

 the benefit of the parasite. 



It is noted in Plowright's monograph that " Mr. G. Massee 

 considers the whole secidium to be a sexual product resulting from 

 the conjugation of two dilated mycelial hyphae in the tissues of 

 the host-plant." This theory of Mr. Massee has not as yet been 

 corroborated. The preparations, on the examination of which 

 it was founded, were handed to De Bary whilst on a visit to 

 England, and he took them back with him to Germany for further 

 investigation. Unfortunately, in the confusion arising from the 

 sadden death of the Professor, the preparations were lost. 



The mycelium present in the leaves of the host-plant (i.e. the 

 pea) resulting from inoculation by the secidiospores, as described 

 above, gives origin to the first crop of uredospores, which are 

 produced singly at the tips of short branches of the mycelium. 

 The epidermis is ruptured, and they appear on the surface as 



