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DIVISION II.-— COURSE OF DEVELOPMENT OF FUNGI. 



adopted. The veil is rent by the upward extension of the pileus, and often, but not 

 always, in such a manner that a portion of it remains behind on the stipe as an 

 annular frill [ring or annulus). 



The veil appears in two principal forms; first, as a membrane running from 

 the margin of the pileus to the surface of the stipe, and therefore does not enclose 

 much more than the hymenia] surfaces, but leaves all the other part free; in this case 

 it may be called a marginal veil, or with Fries velum particle (Fig. 132). Secondly, 

 as a sac which encloses the entire sporophore from its base, and is ruptured at the 

 apex by the unfolding pileus ; in this state it is the velum universale or volva (see 

 below, Fig. 135). 



1. As regards the development of the forms which have the marginal veil 

 only the following special facts have been established by observation. Up to the first 

 formation of the pileus on the summit of the stipe-primordium the phenomena are the 

 same in essential points as in the gymnocarpous forms (Fig. 24 a). The young 



pileus is entirely delimited from the stipe by 

 a transverse annular furrow running along 

 its future hymenial surface. But then the 

 superficial hyphal layers of the stipe and 

 of the young pileus send out numerous 

 branches towards one another from the 

 edges of the furrow ; these unite into a 

 close weft, the marginal veil, which bridges 

 over the furrow and closes it on the outside 

 (Fig. 133). The body of the pileus then 

 developes from the inner hyphal layers of 

 the primordium, those which are nearest the 

 furrow, and chiefly by uniform growth in 

 the direction of the margin and by alternate 

 epinastic and hyponastic growth, as in 

 the species which have no veil. The veil, 

 together with the portion of the stipe in- 

 closed by it, follows the superficial increase 

 in size of the pileus by intercalary growth, till the hyponastic expansion of the latter 

 commences. 



The veil therefore in these cases is, as Bonorden described it, a continuation of 

 the outermost row of cells of the stipe, which grows with the stipe for Mane time by 

 intercalary growth and passes into the margin of the pileus, and conversely a 

 continuation of the outermost hyphae of the pileus passing into the surface of the 

 stipe; it is composed in fact of hyphae of this twofold origin. The structure is 

 differently formed in each separate case, the difference depending on whether it 

 begins to be formed in a somewhat later or earlier stage of the development, and in 

 connection with this whether the hyphae which take part in its formation and run 

 downwards from the pileus have their origin at a greater or less distance from the 

 centre of the pileus, while those which run upwards from the stipe reach more or less 

 of the way to the apex of the pileus ; and also on whether the margin and hymenial 

 projections of the pileus are closely applied to the stipe or are more or less distant 



Fig. 133. Agaricus melUus. Half of a thin median longitu- 

 dinal section through a young pileus before the closing of the 

 veil; h t^fc annular furrow between the pileus and the 

 bounded above by the commencement of the hymenium, else- 

 where by the veil which has begun to develope. After K. 

 Ilartig, Wichtige Krankh. d. Waldb'aume, t. II. Magnified. 



