GKAF ZU SOLMS-LAUBACH— MONOGKAPH OF THE ACETABULARIEtE. 5 



among Algae, e. g. in the formation of the polyhedra of Jlydrodictyon. After a lengthened 

 rest these spores then give rise to the sexual generation of gametes descrihed by 

 Strasbnrger *. 



The formation of resting spores would then he merely shunted to another point of 

 the life-history. We know from de Bary, moreover — and the same takes place in 

 Dasycladus according to my observations — that the zygote, after coming to rest, imme- 

 diately grows out in the form of a cylindrical tube. De Bary could not obtain the 

 normal development of this in his cultures of Acetahularia, but he was able to establish, 

 from specimens collected in the open, that it first forms a basal vesicle as a store for 

 reserve-material, that it then becomes strengthened by repeated diaphysis from this part 

 which remains after the dying of the upper part, and grows into a small plant provided 

 with several whorls of branched hairs. After an uncertain number of diaphyses, the 

 apex of the stalk invested with whorls of hairs arrives at the formation of a cap, which 

 closes the development of the plant with the formation of spores. One finds clearly 

 marked on the stalk of each fruiting specimen, below the terminal cap and at some 

 distance apart, especially after decalcifying it, several whorls of circular scars where 

 the tufts of branched hairs, now fallen off, were formerly situated. 



As regards the development of the complicated structure of the cap there are few 

 observations before us, and these incomplete. However, even so, they show that the 

 naarginal chambers of the cap do not arise as so many separate projections like the hairs 

 of a whorl and subsequently unite, but that the whole margin of the cap first makes its 

 appearance in the form of a continuous cushion below the arched apex of the shoot. 

 With its first formation there coincides that of the chambers and the closing of them 

 towards the vestibules, so that, as I have seen in my spirit-material, they are completely 

 developed when the cap is still in a young state. I have represented in Plate I., figs, i, 

 8, 12, such young stages of the cap in lateral view from the outside and in section. 

 From the outside it appears like a flat, projecting, arched band, bordered above and 

 below by a sharp circular furrow dividing the sectional views of the walls of the chambers 

 by numerous perpendicular lines into almost rectangular areas adjoining each other. Each 

 of these partition-walls corresponds at the stalk end of the band to a line running gradually 

 downward — the projection of the inward fold of the membrane separating off the vestibules. 

 The longitudinal section (Plate I. fig. 8) shows that these vestibules are completely 

 formed, and that the folds separating them at the inner margin are frequently 

 strengthened and irregularly thickened. Prom the central area the margin of the cap 

 appears to be completely separated by the partition, a simple fold of the membrane perfo- 

 rated in the middle. On the other hand, all the differentiations of the wall of the cap are still 

 absent, the outer limit of the chamber seen in section is simply convex, or shows at most 

 a slight depression in the highly arched central portion, where the membrane also shows 

 itself weaker. The whole cap-chamber is completely filled with dense protoplasm 

 without vacuoles. The shallow cavity becomes more pronounced with farther growth, 



* They would represent the rudimeutary sexual geiienition of the plant and be partly male and partly female, as 

 is expressly stated by Strasburger. Willi reference to such a view I am in complete agreement with Falkenberg 



[II, p. 270]. 



