THE PERITHECIUM OP MELIOLA. 13 



of certain phanerogams, 1 or of the pollen mother cells in the anther, 2 

 in so far as the larger cells clearly develop at the expense of material 

 derived from those around. 



The tuft of successful cells thus nourished is, in fact, the " ascogo- 

 nium " of this fungus. At a slightly later stage than the one last 

 figured, the space formerly occupied by the deliquescent remains of 

 small cells is filled with an almost transparent semi-fluid mucus, in 

 which a few bright granules are embedded ; while the lower part of 

 the perithecium contains a tuft of asci in various stages of develop- 

 ment (see fig. 33), and which have evidently proceeded from the large 

 cells of figs. 28 and 31, which have devoured all, or nearly all, the 

 smaller soft cells surrounding them. 



Sections of perithecia at a stage between those shown in figs. 31 

 and 33, have not been obtained, but enough evidence has been secured 

 to enable me to conclude that the asci are the direct result of the 

 transformation of the elongated upright cells of fig. 31, which are 

 nourished at the expense of the cells of the inner layers. Partly from 

 the brittle nature of the outer walls, enclosing a space filled with 

 almost fluid contents, and partly from the extreme delicacy of the 

 young asci, I have been unable to decide whether any distinct branch- 

 ing of the ascogenous cells precedes the formation of the definite asci : 

 probably such is the case. We have now followed the development of 

 the perithecium to the period when it may be considered ripe : a period 

 of some duration, since the asci are continually and successively formed 

 in the tuft for some time. 



Fortunate sections of the perithecium wall at this stage have yielded 

 the following information. In the centre of the apical wall, where a 

 slight protuberance sometimes occurs, the cells of the inner wall are 

 found to radiate towards a pale translucent spot or pore (see fig. 36), 

 and although I have not been able to obtain sections exactly through 

 this, and am therefore unable to affirm positively that it is an actual 

 pore, there seems little doubt that this is at least the weak point 

 through which the spores escape from the ripe perithecium, no doubt 

 forced through by the swelling of the materials around. Bornet 3 

 believes that the perithecium opens by a circular rupture at the base : 

 I have tried to confirm this, but failed, and am strongly persuaded 

 that the apical spot figured is the point of exit for the spores. That a 



1 Cf., amongst others, Strasburger, ' Angiospernien und Gymnospermen.' 

 fl Cf, Strasburger, 'Bau und Wachsthum der Zellhiiute,' 1882, 

 3 Op. cit , p. 261. 



