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H. W. RICKETT 
(fig. 68 D) are considerably spread apart and a single lobe is to be seen 
between them. 
Plant no. 4. The two forward lobes, a and h (fig. 69 yl), are spread 
apart until there is a wide notch between them and they occupy a lateral 
position (fig. 69 B). This notch is filled by a round mass of cells. Two 
new lobes, c and d (fig. 69 C), are formed simultaneously in this notch, at 
first being in a transverse and nearly vertical position. (In the drawing, 
these two lobes appear to be of dorsal origin. This is not actually the 
case, the illusion being due merely to the position in which the plant was 
seen when sketched.) These two lobes are then subjected to the same 
process of spreading, and a few days after (fig. 69 D) a new lobe, e, has 
appeared between them. Three days after this, this lobe has reached a 
considerable size, and there is a new small lobe on either side of it — lobes 
/ and g (fig. 69 E). This occurrence of three lobes, not widely different 
in size, is also very common. In the last stage sketched (fig. 69 7^), a 
single lobe — h — again appears on one side of this "middle lobe," and on 
the other side two small lobes, i and j, are formed at the same time. In 
the subsequent history of this plant, the formation of lobes went on in 
the same way, small lobes succeeding each other rapidly in a very various 
and complicated manner, with no apparent relation to the occurrence of 
branching except sometimes in cases where only a single lobe was formed 
at one time (e.g., lobe e, fig. 69 F). 
Branching always occurs by the division of the apical region. In 
nature it is limited by the short growing season of the plant, and the number 
of growing points found in plants living under natural conditions, as de- 
scribed by Douin, has been referred to above. In culture, however, the 
plants may live indefinitely, and profusion of branching is in keeping with 
the luxuriant habit of the plant as a whole under greenhouse conditions; 
and owing to the rapid elongation of the central axes of the branches, the 
latter are more easily distinguished from each other. By the gradual dying 
of the posterior part of the thallus, branching, under the conditions referred 
to, is an effective means of vegetative multiplication. 
Summary 
1. The spore of Sphaerocarpos Donnellii germinates by means of a 
slender filament of cells, the germ tube, on the end of which, and at right 
angles to it, is formed a germinal disc. The latter structure develops into 
the thallus of the mature plant. 
2. The history of the formation of the germ tube is very variable. 
3. The growth of the germinal disc does not seem to be due to the ac- 
tivity of a single apical cell, except in special cases. It is formed by divisions 
of all the terminal cells of the germ tube, and continues its growth through 
the activity of a group of cells on the margin which remain embryonic in 
character. 
