141 
The Development of the Sporocarp of Pilularia Americana, A. Br. 
By DoucLas HoucGHTon CAMPBELL. 
(PLATE CXLVL) 
Pilularia Americana is by no means uncommon in California, 
and is said to be especially abundant in the Sacramento Valley. 
Last spring a quantity of fresh specimens, collected near Suisun, 
were sent me by Mrs. Brandegee, and as they bore numerous 
sporocarps, in all stages of develoyment, it seemed a good oppor- 
tunity to attempt to clear up some obscure points in the early de- 
velopment of the sporocarps of the Marsiliacez. 
Without microtome sections, it is quite impossible to study 
the earliest stages satisfactorily on account of their small size, and 
because they are completely buried in a mass of hairs that cover 
the growing point of the stem, and all of the younger parts in its 
vicinity. Those hairs cannot be removed from the young sporo- 
carp and interfere very seriously with a clear view of it. 
Our knowledge of the development of the sporocarp of Pilu- 
Jaria is based mainly upon the work of Sachs,* Goebel,t and Ju- 
ranyi,t and that of Marsilia upon Russow’s investigations.§ The 
origin of the sporocarp itself, however, and the formation of the 
cavities in which the sporangia are borne, was not clearly under- 
stood. 
By imbedding in paraffine in the usual way and sectioning 
with a microtome, no trouble was experienced in getting a com- 
plete series of preparations that showed all the details, and the re- 
sults of a study of these is here given. In preparing the speci- 
mens for sectioning, the growing tips of the fruiting plants were 
treated for two or three hours with a I per cent. aqueous solution 
of chromic acid, washed, stained 7” /ofo with alum cochineal, and 
after sectioning, stained on the slide with alcoholic Bismarck- 
brown; my usual method of preparing sections of young tissues. 
* Sachs, Text-Book of Botany, 2 ed., pp. 455-460. 
+ Goebel, « Outlines,” p. 240, foot note. 
_ tJuranyi. The original paper in Hungarian. Reported in Just’s Jahresbericht, 
Jahrgang 1879, p. 416. 
§Russow. Histologie und Entwickelungsgeschichte der Sporenfrucht von Mar- | 
ilia. Dorpat, 1871. 
