RELATION BETWEEX GOXIDTA AXD HTPH.E IX LR'HEXS 175 



original issue] and by the microphotographs. The degree to which 

 the hyphal protoplasm absorbs the stain, compared with the gonidial, 

 permits the possibihty of differential staining, which results in the 

 hyphal protoplasm standing out distinctly against the darker-coloured 

 ground of gonidial substance. 



In the hyphai which are closely adherent to the gonidial cells, 

 lateral offshoots extend from the area of contact and penetrate the 

 cellulose envelope. The hyphse having penetrated the algal cells 

 change in appearance, and I believe that they do not fulfil the same 

 functions. It seems to me necessary to distinguish two types of 

 intra-gonidial hyphse, standing in a close genetic relation to one 

 another. The one to which the term haustorium is especially appro- 

 priate, having penetrated the gonidial envelope in the form of thin 

 threads, encloses the protoplasm of the gonidia in a fine network. At 

 first, following the perforation of the cell-wall, the network of tissue 

 extends only over the surface of the protoplasm. During this process, 

 it is sometimes possible to observe the formation of a very complete 

 network of these hyphal filaments between the cell-wall and the 

 protoplasm. In their further development the intragonidial hyjjhaj 

 extend themselves into the protoplasm itself, piercing it in every 

 direction. This first t3^pe of extremely delicate intragonidial hyphse 

 has the appearance of thin gelatinous branches — to use the accurate 

 expression of Schneider, — which appear to me to be without hyphal 

 envelopes : these thin branches, as may be supposed, are formed only 

 of fungus protoplasm, the cell-wall being either entirely absent or so 

 thin as to be beyond perception. It may be supposed that the hj'phag 

 develop in this type of intracellular haustoria thin threads of proto- 

 plasm, or that the hyphal envelopes are destroyed through the activity 

 of the living gonidial cells, so that only the hyphal filaments remain, 

 unaltered in charactei", but minus the cell-wall. 



Before passing on to the second type of intragonidial hyph<e it is 

 necessary to observe another kind of intragonidial formation, for this, 

 as far as can be determined, appears to have no connection with the 

 intracellular haustoria. At first sight this formation resembles drops 

 of oil adhering to the periphery of the gonidial protoplasm in the 

 shape of tiny ridges. The approach of a light shows them to be of a 

 feeble turquoise-green colour, i. e. their refraction is the same as that 

 of hyphal protoplasm. As far as is known, the literature of lichen- 

 ology contains no description of these. At first I took them for 

 drops of oil, but their persistence in the fixed microscopical prepara- 

 tions after the application of several changes of absolute alcohol to 

 the specimen, followed by xylol, suggested the idea of more closely 

 examining these problematical drops. In the first place, I had to 

 assure m^^self that they were not oil drops. With this object in 

 vievv-, portions of fresh thallus, and also sections cut with a razor, were 

 immersed in absolute alcohol for four days, the spirit being changed 

 daily. Some were then transferred from the alcohol to chloroform, 

 others to ether. The drops suspected of being oil were not dissolved : 

 they did not give an alkaline reaction to alcohol in which they 

 had been kept. A one per cent, solution of osmic acid, in spite of 

 prolonged application, only gave them a brownish tint. This stain 



