490 Osborn. — Some Observations on the Tuber of Phylloglossum. 
in two previous years are visible. Such a single-leaved plant is entering on 
at least the fourth season of its growth. 
Text-figs. 6 and 7 show plants of two and three leaves respectively. 
In Text-fig. 6 three old tuber coats are to be seen. These lie just below 
the surface of the soil, the current tuber being several millimetres deeper. 
The past history of this plant, as shown by its old tuber coats, affords 
a further example of the depth adjustment referred to above. The plant 
was collected July 1918 ; the current tuber, therefore, had been formed in 
the 1917 growing season. That year, the then current tuber, now O.T.j, 
lay close below the surface of the soil, so that the plant produced its new 
tuber, C.T. in the figure, at the end of an elongate stalk. Evidently the 
Text-fig. 5. Single-leaved plant with current tuber c.T. and two old season’s coats O.T., and 
0.t. 2 . This plant is entering on the fourth season of growth. At this date the root is short and no new 
tuber visible (June 13, 1918). x 3|. 
Text-fig. 6. Two-leaved plant with current tuber c.T. at 11 mm. depth, new tuber n.t. just 
forming. Coats of three previous seasons’ tubers (o.t. x , 0 .t. 2 , o.t. s ) are just below ground-level, 
showing depth adjustment in 1917 (July n, 1918). x 3^. 
Text-fig. 7. Three-leaved plant with current tuber c.T. at 9 mm. depth. Old tuber coats (o.t., 
&c.) of four previous seasons at shallower depth (July 11, 1918). x 
lowering of the ground-level occurred some time subsequent to the 1916 
growing season, for lying at the same depth as O.T.j are 0 .T. 2 and 0.T. 3 , 
tubers of two previous seasons. 
Around another plant no less than four old tuber coats were found 
(Text-fig. 7), all lying above the current tuber, again demonstrating the 
burial of the perennating organ to a safe depth. This plant, though it 
possesses but three leaves, was entering on at least the sixth year of its 
growth. 
Such examples illustrate Thomas’s observation on the slow rate at 
which the sporophyte develops. They also show to a slight extent the 
precarious existence led by the Phylloglosstmi in some areas, as it seesaws 
