1889.] MICROSCOPICAL JOURNAL. 177 



on the inside of the terminal part of the old expanded filament, which 

 latter now becomes the exospore. In many species, as of Puccinia 

 graminis, this outer layer of the double wall becomes minutely echinu- 

 late, the markings being essentially of the same nature as those which 

 occur upon many pollen grains and upon .the spores of some of the 

 Ustilaginese. When the spores are mature they either fall off or are 

 pushed off by other spores arising from the spore-bed below. They are 

 now prepared under favorable circumstances to germinate immediately, 

 and, as they may be blown about freely by the winds, this accounts for 

 the rapid spread of the disease among the cereals at this red-rust stage 

 in the development of the fungus. 



Teleutospores. — These constitute the last form of the spore series, 

 and as a rule do not germinate until the spring following their forma- 

 tion, hence they may be considered as the resting spores, the ones in- 

 tended to propagate the new life-cycle which has its beginning in their 

 germination. 



The manner in which they are formed from the vegetative hyphie 

 does not essentially differ from that of the uredospores. Often they arise 

 from one and the same spore-bed or stroma, as in Puccinia graminis, 

 but appearing later in point of time. In those cases in which the teleu- 

 tospores do not rupture the epidermis* they are developed upon new 

 spore-beds. Puccinia coronata may be considered as typical of this 

 class. For the want of fresh young inaterial in others the development 

 of the teleutospores was studied most closely in this species, which 

 doubtless is essentially the same as that exhibited by other species. 



Just previous to the formation of a new sorus, or pustule, several or- 

 dinary filaments meet and coalesce in an intercellular space lying just 

 beneath the epidermis, and become densely protoplasmic. This is the 

 beginning of the stroma or spore-bed. The spores first appear as very 

 short, thick protuberances upon the hyphae which form the upper layer 

 of the stroma. These gradually distend into thin-walled, sack-like 

 bodies, pressing firmly against the surrounding tissues. The body of 

 the spore is early cut oft' from the filament by a cross septum. From the 

 first the young spores are well filled with a finely granular protoplasm, 

 and contain near the central region a much denser body which I take to 

 be a nucleus. When the young spore has attained nearly normal pro- 

 portions, a horizontal septum is throw^n across slightly below the mid- 

 dle, dividing the mother cell. At the period of maturity tiie two simple 

 cells have each acquired a thick reddish-brown wall apparently of two 

 distinct layers, while the old wall of the mother cell which still envel- 

 ops both has become apparently cutinized. 



In regard to the so-called germ pores, I think they are at least of 

 doubtful existence. The pi'ocess of germination, so far as I have been 

 able to trace it in a number of species, consists not in the passing of the 

 germ-tube through an already formed germinal canal. f but by the ero- 

 sion (fig. 2, (5) of the wall from within. J The protoplasmic contents 

 still inclosed in the endosperm gradually dissolves or erodes a passage 

 through the exospore, then expands to form the promycelium, into the 



* For further information regarding these sub-epidermal forms, the nature of the stroma, and a con- 

 sideration of the effect of tension upon the spore form, see " Sub-epidermal Rusts," Bot. Gaz., 1889, 

 p. 139. 



t De Bary, Morphology and Biology of the Fungi, p. loi ; Plowright, British Uredinea; and Ustila 

 ginese, p. 39. 



t Ward, Annals of Botany, vol. ii, p. 220. 



