174 TKE .rurKN.vr, or botan't 



definite sliape of tlie distentions above described when compared with 

 the other hyphal threads, and their constant connection with the 

 gonidia, no alternative remains but to consider these distentions 

 definite organs of the plant, playing an important part in the rela- 

 tionship of the fungus to the green algal cell. Both the internal and 

 external appearance of the gonidia to which these hyphal modifica- 

 tions are found to adhere is very varied : though perfectly normal as 

 far as shape and external appearance are concerned, they are more 

 or less changed internally — some are green, some pale, some devoid of 

 protoplasmic contents. 



In this connection three forms of external contact between gonidia 

 and hypha; may be described : (1) The absence of all superficial 

 attachment or contact in the most literal sense — -described by 

 Schneider as "simple contact"; (2) Contact in the case of the 

 surrounding of the gonidia with budded hyphal cells, a nearer form 

 of contact, and, lastly ; (3) Various stages of attachment, including 

 in their number the union of the club-shaped hyphal distentions 

 when the area of attachment and its strength are particularly signi- 

 ficant. In Schneider's terminology, the second and third cases may 

 be described as extracellular haustoria. The attachment of the 

 hyphiB and gonidia is not confined to the external union of the hyphal 

 and gonidial envelopes, the union is considerably closer. As far back 

 as 1893 Hedlund showed, in relation to some drawings of Lecanora, 

 Lecidla, and Micarea, that the hyphse penetrate the gonidial envelopes 

 in the form of club-shaped distended branches and stimulate the division 

 of the algal cells into two daughter ceils. Schneider gave very con- 

 vincing facts concerning the penetration of the hyphte into the algal 

 cells, giving the penetrating hyphse the name of intracellular haustoria. 

 According to his description, this penetration has been observed, so 

 far, in some specimens of Cladonia, Parmelia, and Stereocaiilon^ and 

 consists in the haustorium piercing the envelope and entering the 

 gonidial cell ; but while this is taking place the hyphte are branching 

 within the cell, between the protoplasmic contents of the cell and the 

 cellulose envelope, but not touching the contents. Peirce in 1899, as 

 the result of his investigations, came to the conclusion tliat the hypha3 

 develop haustoria which penetrate the algal cells and absorb the 

 protoplasmic contents of the gonidia, leaving only the empty cell- 

 wall. 



These intracellular haustoria were also investigated by Elenkin, 

 and are described in a series of papers devoted to the question of the 

 endosaprophytism of lichens, considering as of secondary importance, 

 it is true, those occurring after the disappearance of the gonidial 

 protoplasm, under the action of some enzerae-like substance acting 

 for this purpose. The numerous microscopical drawings which I have 

 made, to be described later, are, I think, sufficient evidence to show 

 beyond all doubt that the hyphse do actually penetrate the gonidia 

 and in doing so take root in live algal cells and not only make their 

 way within the cell-wall to the edge of the protoplasm, but actually 

 penetrate the protoplasm itself, piercing it in all directions by slender 

 processes. I believe this to be sufiiciently proved both by the 

 drawings of microscopical preparations appended to this paper [in its 



