26 PROCEEDINGS OP THE AMERICAN ACADEMY 



iodine brings the asci iuto clear relief. By pressure upon the cover- 

 glass the elements of the hymenium may now be separated, and if the 

 treatment with potassic hydrate and then with tincture of iodine be 

 repeated, and the superfluous iodine washed out with water, the asci 

 appear colored a deep blue, and the paraphyses yellow to brown, and 

 both may be traced to their origin. It is then seen that the subhyrae- 

 nial tissue consists of septate hypha3 a trifle smaller than the medullary 

 hyphas and much distorted by mutual pressure. Even when, as is 

 often the case, the process of clearing has rendered the cell membranes 

 invisible, the continuity of the deeply stained protoplasm shows that 

 both asci and paraphyses arise from the same hyphte. Sometimes a 

 single ascus is seen to be surrounded by a tuft of paraphyses springing 

 from its basal cell, and sometimes an ascus arises as a branch from the 

 basal cell of a paraphysis, (Plate I. Figs. 1-3.) But however the two 

 systems are related in position, they have a common origin from one 

 and the same set of hyphas. This fact seems to militate conclusively 

 aofainst the theory of sexuality, especially when taken in connection 

 with the apparent absence of ascogonic cells, either within the thallus 

 in the neighborhood of young apothecia, or in the tissue of the young- 

 est apothecia themselves, and the absence, as far as I have observed, 

 of trichogyne tips projecting above the surface. 



Sticta amplissima, (Scop.) Mass. 



In this species the general structure of the thallus is essentially the 

 same as in *S'. anthraspis, the slight modifications being due to the dif- 

 ferent nature of the algfe composing the gonidial layer. Whereas in 

 S. anthrasjns they were united into colonies by gelatinous sheaths, 

 here they are seen to be very small, unicellular, and bright grass- 

 green in color, and belong therefore to the chlorophyllaceous genus 

 Protococcus, Ag. The gonidial layer is consequently much more 

 dense, and the medullary layer therefore more closely interwoven, and 

 its hyphte more irregular in their course, than was the case in S. an- 

 thraspis. Let us pass at once, then, to considerations regarding the 

 formation of the fruit. It is not infrequent to find a thallus on which 

 there is no trace of an apotheciura, but which is covered with spermo- 

 gonia in all stages of development visible to the naked eye. Thin 

 sections almost anywhere in such a thallus give the youngest stages of 

 the latter. In places there are seen, with the low power, occupying 

 the lower part of the gonidial layer, pale oval spots. With a higher 

 power, such a spot is resolved into a dense mass of fine branches of the 

 medullary hyphaj, not enclosing gouidia, and therefore appearing pale 



