214 Johnson . — The Procarpium and Fruit 
At the bottom of the thickening a small group of yellowish 
cells is found. Subsequently the thickened portion of the cor- 
tical layer is detached from the tissue lying beneath it, and 
becomes arched to form the pericarp. The group of yellowish 
cells grows and becomes a small hemispherical papilla in 
which one can distinguish two parts ; a lower part, the cellular 
placenta, consisting of cells radiating round a basal cell with 
thicker walls ; and an upper (more peripheral) part, consisting 
of smaller yellowish refractive cells, the rudiments of the 
spores.’ The material upon which Thuret and Bornet’s ob- 
servations were made was collected in 1856, and up to the 
present time Gracilaria has remained one of the gradually 
decreasing number of Florideae whose procarpia are not 
known. The results I am about to describe were obtained 
by the examination of material which had been fixed in picric 
acid and preserved in alcohol by Dr. D. H. Scott, who kindly 
placed it in my hands nearly a year ago. 
Having examined a number of the youngest fruits ob- 
servable without finding a procarpium, and believing that 
Thuret and Bornet would not have failed to see some indica- 
tion of one had it been present in like stages investigated by 
them, I thought that the best procedure would be to take 
filaments bearing the smallest visible swellings, and to make 
successive transverse sections of the whole filament by micro- 
tome. This was done in the case of a large number of 
filaments, but without any sure signs of a procarpium being 
seen. The work, however, was not without result, since it 
seemed to show that the procarpia gave external indication of 
their presence in the form of a swelling. 
I then turned my attention to the lateral swellings, and the 
least of these were selected for section. The structure of the 
procarpium will be best understood by the examination of a 
few typical examples, such as those figured in Plate XI. It is 
to be noted that the whole of the procarpium does not lie in 
one plane, — a condition which increases considerably the 
difficulty of examining it, and of course occasions a variation 
in the figures according to the plane of section. 
