ENDOPHYLLUM EUPHORBIAE-SYLVATICAE 511 



An aecidiospore, on germinating, produces a short basidium about 

 50 ytx. long and 6 ^ wide. Into this flows all the protoplasm con- 

 tained in the aecidio- 

 spore. The passage 

 of this substance can 

 be readily followed 

 owing to the fact that 

 it has a yellow colour. 

 Across the basidium- 

 body three septa are 

 formed which break 

 it up into four cells 

 of about equal size 

 (Fig. 2063, C). Each 

 cell gives rise to a 

 conical sterigma which 

 is about 7 fx long. At 

 the top of each 

 sterigma a spore is 

 developed in the usual 

 manner, i.e. a hilum 

 is first formed and 

 then a spore-body, the 

 latter growing in a 

 direction which is in- 

 clined at an angle of 

 about 30° to the axis 

 of the sterigma (F, a). 

 The spores are more 

 or less pear-shaped 

 but flattened or 

 slightly concave on 

 the side toward the 

 hilum ; and their 

 length is 9-10 /i. The 

 four spores of a basi- 

 dium commence to 



Fig. 206. — Endophyllum Euphorbiae-sylvaticae. De- 

 velopment and discharge of basidiospores. A, leaf 

 of Euphorbia amygdaloides with numerous aecidia. 

 B-E, aecidiospores which have germinated and 

 have produced basidia. B, basidiospores develop- 

 ing, each one a few minutes old, the end one the 

 oldest. C, all the basidiospores are full-grown. 

 D, optical section through a basidium in which the 

 protoplasm is passing up the sterigmata into the 

 spores. E, a basidium discharging its spores ; 

 one spore has gone, and the end one with a drop of 

 water excreted at its hilum is just about to be 

 discharged. F, successive stages iri the discharge 

 of a single spore ; a, sterigma and lateral view of 

 a spore showing the hilum ; b, a drop has been 

 excreted from the hilum ; c, the drop has grown 

 to its maximum size ; d, the spore with the drop 

 clinging to it has just been discharged, leaving the 

 sterigma uncollapsed. A, natural size ; E-F, 

 magnified 587. 



