OF ARTS AND SCIENCES. 27 



in comparison witli the surrounding tissue. The cells com[)osing these 

 hyphae are copiously filled with small drops of oily matter. The mass 

 when first plainly visible measures about G8 jx in diameter. In a 

 slightly later stage the mass has become lengthened considerably in a 

 direction perpendicular to the surface, and is now flask-shaped, the 

 neck — a solid cylindrical shaft of hypha3 — being almost as wide as 

 the spherical mass below, and extending through the gonidial layer 

 very nearly to the surface. Later stages show that this mass, the 

 young spermogonium, now increases very rapidly in size, the centre 

 however occupying about the same depth in the thallus. From this it 

 follows that the mature spermogonium occupies nearly the full depth 

 of the thallus, extending as far towards the lower as towards the upper 

 surface. As the young spermogonium grows, the hyphae composing 

 what I have called the neck become more and more merged in the 

 spherical part of the spermogonium, until at maturity the latter pos- 

 sesses no real neck, it is no longer flask-shaped but spherical, and its 

 upper surface is so slightly beneath the surface of the thallus that the 

 absorption of cell-membranes and the formation thus of a minute pore, 

 suffices to establish a connection between the interior of the now 

 hollow spermogonium and the outer air. As in S. anthrasj^ia, the 

 mature spermogonium is almost filled with jointed arthrosterigmata 

 growing out from the walls, and bearing countless rather large oval 

 spermaiia. 



I have said that some thalli produce spermogouia almost exclusively ; 

 as might be inferred, others are found covered with apothecia only. 

 Near the centre they occur so plentifully that they almost hide the 

 thalline surface; toward the margin they occur more sparingly and in 

 younger stages, while near the extreme edge they are wanting, and a 

 very few scattered spermogonia are found. If thin sections are made 

 in that part of the thallus where apothecia in great numbers are just 

 visible with the hand-lens as minute elevations of the thalline surface, 

 we find in considerable numbers, in the lower part of the gonidial 

 layer, small, irregularly spherical masses of hyphae, displacing the algae. 

 These hyphaj are filled with small oil-drops, the masses measure from 

 60 to 70 /A in diameter, and, in fact, both in position in the thallus 

 and in general appearance, they remind us of what we found to be the 

 earliest stages of spermogonia. Closer examination, however, shows 

 points of difference. In the first place, they occur in a thallus almost 

 destitute of spermogonia ; tne masses are also more decidedly spher- 

 ical, nor is there ever seen in later stages the lengthening upwards 

 which always occurred in the young spermogonia; and, finally, the 



