Osborn . — Some Observations on the Tuber of Phylloglossum . 493 
was evidently such a leaf on which the cell mass was small in size, but had 
almost obliterated the scar formed when the leaf was detached. This scar, 
somewhat exaggerated in the figure, was so minute that it was not recog- 
nized when first examining the leaf. 
Two further plants of interest were found in the field that season. One, 
a single-leaved plant, had suffered an injury about 1 mm. above the soil. 
The leaf was broken through and lay along the soil, but was not actually 
detached. The wounded surface had healed over, and a new tuber was 
forming normally (Text-fig. 13). The broken leaf, however, had not died, 
but was turgid and green beyond the zone of injured tissue. It had, more- 
over, begun to form a cell mass upon the lower surface. The second plant 
was a three-leaved one, one leaf of which had been broken and lay along the 
soil. Again the wound had healed on both sides of the injury, and the 
damaged leaf had developed a cell mass near to the proximal end, from the 
surface of which several rhizoids arose (Text-fig. 14). 
The growing season for Phylloglossum was almost over in 1917 when 
these observations were made, so that experimental work was impossible. 
The two leaves shown in Text-figs. 9 A and 11 A, however, were laid upon 
soil from the locality in which they had been found, placed in a Petri dish, 
and kept moist in the laboratory. After about seven weeks it became 
necessary to stop the experiment as the leaves were beginning to decay. 
That shown in Text-fig. 9 A had developed a further swelling, irregularly 
spherical, closely connected with the first (Text-fig. 9 B). The new swelling 
was opaque, white, and bore short rhizoids. The other leaf (Text-fig. 1 1 A) 
showed an unexpected development. No stalk-like structure had formed, 
but the original cell mass was considerably enlarged (Text-fig. 1 1 B), and 
a minute green leaf-like scale (/) had developed. 
Experimental Development, 1918. 
In 1918 five series of experiments upon the production of tubers by 
detached leaves were carried out in the laboratory, the results of which are 
here given in tabular form, and are further discussed below. 
Series 
Letter. 
Date Expt. 
started . 
No. of 
Leaves. 
No. formed 
single tuber. 
No. formed 
single cell 
mass. . 
No. formed 
several cell 
masses. 
No. died of) 
without apparent 
growth. 
A. 
13. VI 
8 
1 
(1) 
6 
— 
B. 
ir. VII 
8 
7 
1* 
— 
— 
C. 
21. VII 
10 
5t ( + 3) 
(D 
i§ 
— 
D. 
21. VII 
10 
1 
I* (+ 2) 
1 
5 
E. 
13. IX 
12 
— 
5 
. — 
7 
48 
14 ( + 3) 
7 ( + 4) 
8 
12 
f In one of these cases two tubers formed (Fig. 18 d). 
* Leaf died off before experiment finished. 
§ Developed two ‘ leaflets ’ only. 
The numbers in brackets refer to leaves fixed for microtoming before fully developed. 
