The Formation of the Capillitium in Certain 
Myxomycetes. 
R. A. HARPER AND B. O. DO 
With Plates I and II. 
BY 
HE nature of the capillitium as an intraprotoplasmic secretion was first 
X recognized by Strasburger (43), who noted the fundamental differences 
between the method of its formation and that of the structurally and 
functionally similar elaters of the Liverworts, &c. Strasburger described 
the capillitium of Trichia fallax as originating in vacuolar spaces in the 
cytoplasm which elongate and take on the tubular form of the young 
capillitial threads. He described the formation of the wall and spiral 
thickenings as due to the deposition of granules, which he characterized as 
microsomes of the membranogenous type, such as he believed are also 
found in the formation of the cell-plate in cell-division in the higher plants. 
The essential point in his description is that the spirally thickened capillitial 
threads are not elongated cells, but are intracytoplasmic secretions or 
depositions, and in this he has been confirmed by subsequent observers so 
far as they have considered the point. Strasburger does not figure the 
earlier stages in the appearance of these capillitial vacuoles nor their 
elongation to form tubular threads. 
The examination of material prepared for the study of nuclear division 
and spore formation led to the discovery of well-marked aster-like figures 
at certain stages in the formation of the capillitium, which seem to throw 
light on the general nature and functions of fibrillar structures in the cyto- 
plasm. Such figures were first observed by Miss A. L. Dean, working in 
the botanical laboratory of the University of Wisconsin, and a preliminary 
report on the evidence that these figures are due to cytoplasmic streaming, 
and are to be associated with other fibrillar structures duetto streaming, such 
as are found in the storage cells of Pyronema , &c., was made at the meeting 
of the Botanical Society of America in 1907 (20). These figures were 
described as aster-like radiations about the circular cross-section of the 
forming threads. 
Kranzlin (28), on the basis of studies on Oligonema nitens and Arcyria y 
has described the capillitial threads as arising from centrosomes, and has 
[Annals of Botany, Vol, XXVIII. No. CIX. January, 1914.] 
B 
