380 PEIRCE: ForcisLeE DISCHARGE OF 
the soil, turgidity will always develop. The structure of these 
turgid parts demands a moment’s notice. The antheridial patches 
of Asterella, as shown in fig. 3, are somewhat raised above the 
general surface of the thallus. The tissue composing and under- 
lying this elevation is very different from that elsewhere. A sec- 
tion through one of these antheridial patches parallel with and 
below the surface of the thallus, shows that the thallus is com- 
posed in the main of moderate sized cells, containing many chloro- 
phyll grains and with small intercellular spaces between, while 
the part of the thallus where the antheridia are consists of much 
larger cells, with far fewer chlorophyll grains, cell-walls no thicker, 
and (when the tissue is full of water) there are no intercellular 
spaces. The distribution of these tissues is plain to the naked 
eye, for the part under or among the antheridia appears quite col- 
orless compared to the adjacent tissue rich in chlorophyll. /%- 
4 shows such a section. The part of the section outside the 
bounding line consists of chlorophyll-containing rather small- 
celled tissue. Within the line one sees holes of various sizes and 
shapes between which are comparatively large, thin-walled cells 
pressed close together owing to their turgidity. (I sectioned a 
thallus from very wet soil.) In the spaces a and 6 were anther- 
idia, in the other spaces there were none. Some of these spaces 
are nearly obliterated, as those lettered c and d show. /#g- 5 
is an enlarged drawing of the part a of jig. 4, that is, a cross sec- 
tion of an antheridium enclosed in the turgescent nearly colorless 
tissue of the cushion. The cells forming the wall of the anther- 
idium are shown in outline (a), the adjacent and closely pressing 
vegetative cells are only partly shown (4), while the blank central 
portion (c) represents the mass of antherozoids enclosed in slime, 
forming the greater part of the antheridium. ig. 6 is a longi- 
tudinal section of an antheridium, a section at right angles to the 
surface of the thallus, similarly lettered. All the sections are free 
hand, and the one shown in fig. 6 does not show in quite true 
proportions the opening of the chamber in which the antheridium 
lies. The tissue within the bracket d is composed of compara- 
tively small cells, rich in chlorophyll, the tissue bracketed ¢ is 
composed of large cells, comparatively poor in chlorophyll, and 
capable of great changes in volume. It is precisely this compat 
