ON THE MORPHOLOGY OF HEMILEIA VASTATRIX. ^ 



whole process normally advances to completion, while the Teleu- 

 tospore is still attached to the spore-bearing head, though 

 detached specimens germinate quite readily in water on glass 

 slips. 



When the promycelial tube has attained a length of 

 about six to eight times that of the Teleutospore it becomes 

 divided by transverse septa into four subequal cells (figs. 42~ 

 45), each of which receives its share of the orange- coloured 

 contents, which have passed along the tube from the spore. In 

 specimens grown on glass slips under cover the promycelium and 

 chambers are much longer (figs. 45, &c.) than those found on the 

 leaves, and the tube may be curved and delicate in the former 

 case, whereas in the latter the promycelium stands up stiff and 

 straight into the moist atmosphere. This may be compared 

 with what occurs with Uredospores germinating on glass and 

 leaves. 



The promycelium fully formed, each of the four cells (nor- 

 mally) sends forth a slender process, into the cavity of which 

 the coloured contents pass (fig. 45) ; the process from the 

 upper cell is simply a continuation of its apex ; those from the 

 sides of the lower cells spring from beneath the septa. The 

 free terminal portion of each of these four outgrowths now swells 

 into the form of a small subglobular conidium, which receives 

 the remaining contents, and at last is simply attached by one 

 point to the constricted end of the branch which produced it 

 (figs. 42 — 46), and may be detached with the greatest ease. 



This conidium, abstricted in this manner from the promy- 

 celium, is much smaller than the Teleutospore; it is usually 

 subglobular, but at times subreniform or ovoid in shape, and 

 is filled with the usual orange-red, granular protoplasm (fig. 46), 

 enclosed in a delicate, smooth envelope. During* the formation 

 of the structures just described — i.e. during the later stages of 

 its germination — the walls of the Teleutospore and promycelium 

 become collapsed (figs. 42 — 46, &c.), and, being very tran- 

 sparent, are not easily discovered. 



The Conidia germinate readily in water (and, indeed, even 

 while attached to the promycelium), and may produce a long 

 delicate tube (fig. 46 d) very rapidly ; as a rule, however, after 

 forming a large central vacuole, the endospore protrudes slowly 

 (fig. 46 a) as a blunt, thin-walled, finger-like process, which 

 attains a length of some four times the diameter of the coni- 

 dium, and then shrivels up and dies. This very simple and 

 transient germination is all T have been able to induce, either 

 on glass or living leaves. 



The production of Teleutospores, &c., appears to be the last 

 act of the mycelium within the leaf, and the brown, shrivelled 



