36 
DR. MINKS ON THE MICROGONIDIA OF LICHENS. 
existence, for the hyptra cell of the lichen, as the gonidial cell 
together with each cell of the lichen, is capable of pysiological 
activity, such as appertains to all vegetable cells that contain 
chlorophyl ; and as regards systematic botany the presence of 
gonidia appears to be the criterion between these two great vege- 
table kingdoms, for the microgonidia are characteristic of lichen 
ccdls only. 
The greater part of lichens, if not all, do not grow by a simple 
increase of the cells of the two systems of tissue ; the development 
of the gonidial tissue results from the hyphge tissue and never the 
reverse. The series of microgonidia running through the axis of 
the hypha threads and filling up by conglomeration the gonidial 
cells is in fact a series of gonidia in the embryonic stage. The 
moment the microgonidia secrete a membrane they become true 
gonidia, which commence, either in the mother cell or after its 
breaking up, to take on the known form, producing at the same 
time new microgonidia. There is no doubt that the development 
of the gonidia issuing from the hyphaB cells or from the gonidial 
cells does not take place without order in lichens, but either one 
predominates or the other, according to certain fixed rules for 
certain ends. 
It is evident that the gonidia cannot augment exclusively by 
division or progemmation as do the hyphse, there must be some 
other source, to the present invisible, whence issues the hyphoidal 
tissue. The new tissue, the hypheme, is, I believe, the most deli- 
cate in nature, and as far as is known, the lenticular cells of this 
tissue are excessively minute, and their mutual connexion exists 
only at a single point. The study of the hyphhie^ the existence of 
which is already difficult to establish, presents inexpressible 
difficulties. 
The absolute necessity of the hypheme is manifest in certain 
phenomina of growth, especially in the work of reproduction. 
Primarily the hypheme accompanies or pursues each reproductive 
extension of the Mallus which in the same lichen may partake of 
many types, and exhibit itself in the greater part of lichens in 
enormous quantities. In each case of reproduction it establishes 
an initial point due to an elementary organ, arising it may be from 
the gonohypheme, or the gonideme, or the hypheme, throwing out, 
nevertheless, only the basis of the gonideme, with which is asso- 
ciated the maternal hypheme to be completed by the germ of the 
hyphoidal tissue, the reproductive lichen organ. 
This co-operation on the part of the hypheme is an evident fact 
amongst some blastemes, but especially amongst the hormospores 
discovered by me, and principally amongst the mecaspores, which 
uniquely, by means of a hypematic capsule, become capable of re- 
producing a lichen. Unfortunately I have not been able to do 
more than roughly sketch the activity of the hypheme in my draw- 
ings for a magnifying poTver of 2,000 diameters would be necessary 
for the purpose of properly drawing it. 
