CHAPTER V. — COMPARATIVE REVIEW.— ASCOMYCETES. — SCLEROTINIA. 219 



peripheral mass the elements of which originate in the periphery of the primordium 

 as branches of the stout medullary hyphae. The small central bundle is short, the 

 peripheral hyphae are longer in proportion as they are nearer to the circumference, 

 and, like the periphyses of the Pyrenomycetes, their extremities converge towards the 

 median line, and thus a narrow depression is formed at the apex of the whole which has 

 been noticed before on page 52. No other decided difference of structure is to be observed 

 even at this time between the two kinds of hyphae, and during the subsequent growth 



wmRP 



FIG. 104. Sclerotinia Sclerotiorum. Thin ver- 

 tical section through the periphery of a sclero- 

 tium which has been kept moist and is ready 

 to develope ; beneath the black rind is the 

 primordium of a sporocarp. The dark angular 

 bodies are calcium oxalate. Magn 150 times. See 

 also Fig. 14. 



FIG. 105. Sclerotinia Sclerotiorum. Median section through a 

 young sporocarp which is bursting through the rind. Magn. 90 

 times, but completed from higher enlargements. 



of the whole body all possibility of distinguishing them ceases. But it is not improbable 



that the difference reappears with the formation of the ascus, in other words, that the 



hyphae which have proceeded from the primordium are the ascogenous hyphae and 



the primordium is therefore an ascogonium, while the envelope-apparatus of the 



sporocarp with the paraphyses comes from the peripheral hyphae ; and thus the 



young sporocarp contains from the first the two elements side by side, though they 



are not anatomically different. The original structure 



of the primordium is obscured after the emergence of 



the sporocarp, but its place usually continues to be 



distinctly marked by the brown colour of the walls of 



the medullary cells at its circumference ; this however 



may often ultimately spread to the primordium also. 



The number of primordia in a sclerotium is always 



much larger than that of the sporocarps which are 



matured ; many are obliterated by their peripheral cells 



turning brown or are destroyed by the emergence of 



neighbouring sporocarps. 



Sclerotinia Fuckeliana shows phenomena of 

 development quite similar to those which have been 



described ; but there is one difference which adds greatly to the difficulty of obser- 

 vation : the primordia are not formed inside, but on the surface of the sclerotium. 

 A thin bundle of hyphae from the medullary tissue bursts through the rind and 

 developes on its outer surface into a dense round coil, the central part of which 

 is like the primordium of S. Sclerotiorum and is surrounded by the peripheral hyphae 



FIG. 106. Sclerotinia Sclerotiorum. 

 Sclerotium with eight sporocarps of 

 different ages ; natural size. 



