12 
Harper and Dodge . — The Formation of the 
root-tip cells numerous delicate protoplasmic streams can be seen flowing 
lengthwise of the cells curving out around the nuclei, &c., their distribution 
thus corresponding closely to that figured by Nemec (38) for his fibrillar 
systems in the cells of the root-tips of Allium , certain Ferns, and other 
types. 
It seems probable that the fibrillar structures described by the 
Bouins (4) and others are in the same way evidence of the movement of 
food-stufifs in definite directions in the embryo sac. M. and P. Bouin (3) 
regard the ergastoplasm as identical with the mitochondria of animal eggs, 
without changing their opinion as to its fibrillar structure and its relation 
to the metabolic processes going on in the embryo sac. They accept as 
a basis of their interpretation of the ergastoplasmic structures in the embryo 
sacs Garnier’s (15) interpretation of the fibrillar elements in the serous 
gland-cells of animals, which are apparently quite similar in their appear- 
ance. It is to be noted, however, that Orman (39), on what appears to be 
not very adequate evidence, concludes that the ergastoplasm consists of 
lamellae and not fibrillae. 
The barrel-shaped systems of fibrils, which are present in the storage 
cells from which the paraphyses arise in Pyronema (22), afford a case in 
quite a different connexion in which the suggestion is very strong that the 
fibrils represent the lines of transportation of food materials from one cell 
to the next. 
The evidence that these radial fibrillar systems are due to streaming 
seems quite convincing, and that cytoplasmic fibrillar structures in general 
arise by streaming seems by no means impossible. Biitschli (5, 6) has 
advanced two conceptions as to the astral figure. First, it may be due to 
diffusion streams, and, second, it may be due to tensions set up about 
a region of contraction. The possibility that such figures as we find about 
the capillitial vacuoles may originate as a result of the pull about a con- 
densation centre must certainly be considered. Such radial systems seem, 
in fact, to illustrate especially well Biitschli’s conception that the visible 
elements of an aster are due entirely to a rearrangement of the cytoplasmic 
elements, which results from centrifugal tensions set up about the centro- 
some. There is no question that the rays in these Slime-moulds are actual 
fibrils, and when cut transversely appear as points. It is not so certain, 
however, that such an appearance is inconsistent with the view that they at 
least frequently lie at the angles of intersection of meshes and alveolar 
membranes. The fibrils are certainly not entirely free in a homogeneous 
ground substance. The structure of the cytoplasm in these Slime-moulds is 
conspicuously reticulated and spongy rather than alveolar alone, but just 
how the radial fibrils are related to the remaining elements of the spongy 
colloidal mass is not easy to determine optically. 
Biitschli’s radial figures, which are formed about air bubbles in cooling 
