282 Beer . — On the Development of the Spores of Ricci a glauca. 
are often at first inseparably united, but which nevertheless have a distinct 
origin. In his examination of Riccia Strasburger found that by bursting 
the special-mother-cell wall by means of pressure he was able to separate 
the spore-protoplast, surrounded by the first spore-wall, from the special- 
mother-cell wall. Moreover, he states that the folds of the first spore-wall 
never quite reach to the summits of the indentations in the special-mother- 
cell wall h If this were actually the case it would, as Strasburger clearly 
saw, form strong evidence in favour of the independent origin of the two 
layers. My own preparations, however, do not confirm Strasburger in this 
respect. Wherever the section is accurately longitudinal (as regards the 
fold of membrane and the indentation) it can be distinctly seen that the 
first spore-wall lines the indentation in the special-mother-cell wall to its 
very apex. Where, however, the section has cut the fold of the first spore- 
wall somewhat obliquely the true relations of this fold to the indentation 
are not always at once clear. 
From what has been said above it will be seen that the evidence which 
we possess is entirely inconclusive and that neither Leitgeb nor Strasburger 
were justified by the facts in assuming a definite position. 
A study of the microchemical reactions of this wall furnishes no assist- 
ance in deciding this question. The whole behaviour of the wall indicates 
that it is cuticularized from a very early period ; whether there is a basis of 
cellulose, callose, or pectose preceding or underlying the cuticularization was 
not apparent from any of my experiments. 
It may be mentioned here that after treating sections of older spores 
with a mixture of chromic and sulphuric acids and then (after washing) 
adding chlor-zinc- iodine it can be seen that the first spore- wall has a rather 
densely laminated structure (Figs. 24 and 25). 
Not long after the first spore-wall has been formed a deposit of 
mucilaginous substance can be seen at the equatorial rim 1 2 of the spore 
(Fig. 20). As Leitgeb correctly stated, this mucilage has the same chemical 
and physical properties as the secondary thickening layers of the special- 
mother-cell wall ; that is to say it is composed of callose. Leitgeb further 
supposed that this mucilage was derived from the special-mother-cell wall, 
a portion of which wandered through the first spore-wall at the equatorial 
region. The first spore-wall is, however, always continuous and never inter- 
rupted at any spot, as Leitgeb thought was sometimes the case (Figs. 20, 21). 
Strasburger considered the mucilage to be a part of the first spore-wall ; his 
chief reason for doing so was that he found that this wall and the mucilage 
were not sharply marked off from one another at the equatorial rim. I find 
that the mucilage is formed later than the first spore-wall, that the callose 
1 Strasburger, 1 . c., p. 109. 
2 Leitgeb called this equatorial rim a ‘ Saum,’ whilst Strasburger wrote of ‘ einem aquatorialen 
Fliigel, das heisst einem an der Grenze von Riicken- und Bauchflache verlaufenden Saum.’ 
