SOME ACCOUNT OF POLYSTIGMA RUBRUM. 33J 



attached to the tree, ahout the time when the greater part of 

 tlie spermogones are com})leting their development. They are 

 to be found on the same surface on which the spermogones 

 have their mouths, as early as the end of July. They appear 

 at first in a very similar manner, as closely- wound balls of 

 hyphse, of a deep-red colour, very much smaller than the 

 mature spermogones, but more numerous, and distributed 

 evenly over the stroma without regard to the spermogones. 

 Within each mass one of the hyphce differentiates itself from 

 the rest, becoming thicker and spirally twisted, and sending 

 out a prolongation which pierces the stroma and projects 

 above its surface as a thick thread, surrounded at its base by 

 more delicate threads. The spiral hypha is called an asco- 

 gonium, and the projecting thread a trichogyne. Frank 

 often found the sperraatia clustered in heaps round the base of 

 a trichogyne, and occasionally detected one closely united with 

 its apex. In such cases the spermatiura was observed to 

 undergo a change ; the contents appeared to pass out ; it be- 

 came full of vacuoles, and its outline irregular and by degrees 

 almost imperceptible, while the uou-copulated sperraatia re- 

 mained full and regular. Fisch was not able to convince him- 

 self of the process of fertilisation, as Frank has done, but if we 

 consider the striking homology between the organs just de- 

 scribed as ascogonium and trichogyne, and those known 

 by the same names among the Lichens (for Avhich see the 

 'Quart. Journ. ofMicroscop. Science/ xviii, 1878, p. 440, and 

 especially PI. XX, figs. 1 — 3) ; if, moreover, we regard the 

 simultaneity of their formation with the time of greatest de- 

 velopment of the sperraatia, the enormous numbers of the 

 latter, which render fertilisation almost a certainty, their curious 

 hooked forra by which they are enabled to hang on to the 

 trichogyne on the under surface of the leaf, we can, as Frank 

 says, have little doubt of the purpose which these oi'gaus serve. 

 In these respects, and in the position of the male and female 

 organs on the lower surface, together with the mucus in which 

 the sperraatia are involved, which protects them from being 

 washed away by the rain or dried up prematurely by the sun^ 



