362 



MELA.MI'SoKKLLA 



witches : -bi ms on the Fir, the infected buds producing dense clusters of 



small leaves which are not pseudo-distichous as in the norma] shoots) but 

 spirally arranged, moreover they are not evergreen, but fall off in August. 

 <»n these leaves the spermogones and secidia are seen in June; and the 

 secidiospores infect the second host and produce uredo-sori in 10 — 14 day-. 

 It will he seen that the teleutosj .ores found in spring do not belong to the 

 same generation as the uredospores found in the following summer. 



The mycelium of hot h stages is perennial, so long as the host survives, 

 this being the only known instance of such a state of things: for this 

 reason the parasite can maintain itself on either the Fir or the other host 

 quite independently. On the Fir, it produces in time large cankerous 

 growths. There is some evidence that a specialisation into biolog 

 : ces on different species of Alsineae has begun. In the latter the 



Fig. 270. 31. Caryophyllaeearum. a, cells of the peridium of a uredo-sorus, 

 on Stellaria graminea, showing the opening pore bein^ formed beneath a 

 stoma, seen through the epidermis, x 600 ; b, an epidermal cell of S. 

 nemorum, containing teleutospores (after Fischer) x about 400 ; c, attacked 

 leaf of .S'. graminea, slightly enlarged; d, one young and two mature 

 uredospores, x (500. 



mycelium grows up with the young shoots and gradually spreads upwards 

 into every leaf, making the leaves in many cases smaller, but not much 

 different in colour. I have seen a few uredo-sori on the upper side of the 

 leaves, and even on the sepals of Cerastium. 



The peridium of the uredospores is formed of a definite hemispherical 

 pseudo-parenchymatous layer, one cell thick, most of the cells being 

 polygonal by mutual pressure, nearly smooth, and containing at first a 

 little of the same yellow oil as the uredospores. It bears a very close 

 resemblance in texture to that round the uredo-sori of Pucciniastrum 

 Circaeac, Mi'/'*;,,,, Blerhai, Credinopsis JUieina, and their allies. 



The hetercecism of this parasite was established by Fischer in 1901 

 (Zeitschr. f. Pflanzenkr. xi. 321) ; the result was attained only after a long 



