SUPERFICIAL FUNGI. 367 



branch being" roUetl up in a spiral Ifashion, and giving the mem- 

 brane a very characteristic appearance. 



The developing asci cause the central part of the membrane 

 to become arched, and the spores finally dehisce at the apex 

 through a circular pore. 



Still a third type of membrane is to be found in the genus 

 MicrothyricUa ; the mature membrane in this case differs con- 

 siderably in appearance from the one just described, although it 

 is really only a variation oi the net-like structure. It originates 

 in a net-like branching- of the hyphae, but after the intercalary 

 spaces have all become filled up by lateral branches the straight 

 lines of the component hyph?e are lost, and the membrane has a 

 parenchvmatous appearance. The cell-walls, however, never 

 become thickened as they do in the " net-like '" membrane, and 

 they are usually yelloAv or yellowish-brown, never greenish. 



This " net-like " development of the perithecial membrane 

 is so characteristic and so clistinct from the radial structure of 

 genera, such as Asferijia, that Theissen considers that they should 

 be placed in a separate family, which he calls the Hcmispharicece. 

 There are two distinct families with hemispherical perithecia, the 

 Microtliyriacecc, with the inverse radial structure, and the Hemls- 

 phccnacecc, in which the perithecial membrane originates in a 

 net-like brandhing of hyphse ; the latter family consisting of two 

 sub- families, in the first of which the net-like structure is more 

 or less evident, and in the second the mature membrane is 

 ]>arenchymatous in appearance. 



In a species originally described as an Astcriiia. there is still 

 a third type to be discussed. In the Microthyriacecc the spore 

 on germination forms a thread-like mycelium, consisting of 

 branched hyphre, with a single row of cells. The thyriothecia 

 originate from the hyphae as independent bodies, and they are 

 totally different from the mycelium in origin, growth, and struc- 

 ture. 



The development of the Trichopcltacccc, as they are now 

 called, is entirely different. From the germinating spore there 

 develops through the repeated branching of the hyphae a circular, 

 one-layered membrane. This either grows in a single direction 

 and becomes ribbon-like in form, or the disc continues for some 

 time to enlarge, and then developes ribbon-like bodies on several 

 sides. 



The ribbon-like bodies consist of a central axillary strand of 

 elongated cells, which are somewhat broader afid more variable 

 than those of the peripheral zone where the narrow, straight 

 hyphse are nearly parallel to one another, and at right angles 

 to the margin and to the axial strand. The course of these peri- 

 pheral hyphae can easily be traced; when one of the stout 

 hyphae of the axis bifurcates, one of the branches continues 

 in the same direction as the main hyphae, but the other takes a 

 sharp curve outwards, and by repeated branching produces the 

 narrow peripheral hyphae ; the first of the branches which was 

 not curved soon again bifurcates, and the process is repeated. 



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