1898-99.] | MORPHOLOGY OF THE CENTRAL CYLINDER IN THE ANGIOSPERMS. 611 
Merker.” Van Tieghem® examined the anatomy of a number of 
species of this genus in connection with his essay on Polystely. 
Certain species, G. cordifolia, G. monoica, and G. prorepens possess mono- 
stelic central cylinders which are quite pithless. In these species this 
state of affairs is sometimes departed from in the leafy stems (as distin- 
guished from the creeping rhizomes) where the stele may occasionally, 
according to Van Tieghem,” flatten out and bifurcate in the usual 
polystelic fashion. The strands however in these cases are never more 
than two. In G. magellanica and other species, the young stele bifur- 
cates a certain number of times in the epicotyledonary region and 
becomes polystelic. In species with large stems, ¢¢., G. macrophylla, 
etc., the bifurcations are described by Van Tieghem” as being exceed- 
ingly numerous. 
Through the quite exceptional kindness of Dr. D. H. Scott, Director 
of the Jodrell Laboratory, Kew, the writer has had the opportunity of 
examining material of seedlings of Gunnera scabra. As Dr. Scott 
himself has an article on this species in preparation, it will be possible 
only to refer in a passing manner to the writer's own observations. All 
that need be said in this connection is, that the epicotyledonary system 
of G. scabra is primitively tubular, as are those of Pterzs aguzlina and 
Primula farinosa ; and that it is further characterized by the same foliar 
gaps subtending the points of leaf-traces. .It resembles, moreover, 
Primula japonica and P. farinosa, in the absence of internal phloém, on 
the inner side of the young stele. So far as may be judged from the 
development of these species, the polystelic Gunneras do not differ in 
the nature of their young stelar system from the other polystelic forms 
examined by Gwynne-Vaughan and the writer. They resemble the 
polystelic Primulas in showing developmental evidence that the so-called 
polystelic condition is derived from a primitively so-called astelic 
arrangement of the vascular tissues. 
SAXIFRAGACEA®: 
The writer has found the so-called phenomenon of Polystely to be 
present in the Saxifragaceez. As one of his students is working over 
the anatomy and development of the stem in this order, it will be 
necessary only to refer to certain features having an immediate bearing 
on the present research. 
27. Merker, Gunnera Macrophylla. Inang. Diss., 1888, Marburg. 
28. Op. Cit., p. 307. 
29. Op. Cit., p. 308. 
30. Op. Cit., p. 309. 
