242 
Welsford . — Trichodiscus elegans , Gen. et Sp. Nov. 
germinate in the mother-cell. In Trichodiscus elegans the various phases 
of reproduction occur simultaneously, and sometimes very close together 
on the same plant. For instance, one of the figures represents a group 
of cells in which there is a mature sporangium containing gametes, and close 
beside it a younger sporangium, which after one division of its contents has 
ruptured and set free an asexual daughter- cell. Growing close to these is 
the group shown in another figure, in which there are three young sporangia 
before division, and one in which the contents, while still within the cell- 
wall, have developed into a thallus. In no case was it found possible 
to distinguish in any way between those cells which would eventually 
contain either gametes, asexual daughter-cells, or young plants ; the close 
agreement of their initial cells suggests the possibility that they are 
homologous structures. 
The changes of environment which account for Klebs’s results, and 
which Lang (4) suggests determines whether the sexual or asexual character 
of a cell is latent or patent, are in this case absent. Here we have both 
gametes and asexual cells arising under precisely similar conditions. In 
this case it appears, therefore, that we must look for some stimulus other 
than the ordinary environmental conditions suggested by Klebs. Such 
a stimulus is probably closely connected with the nutrition of individual 
cells, and may be due to some subtle osmotic change acting from within 
instead of from without, as Livingston (5) has suggested is the case in a species 
of Stigeoc Ionium. 
Summary. 
1 . The alga Trichodiscus elegans , a member of the Chaetophoraceae, 
is described. 
2 . In Trichodiscus elegans both sexual and asexual cells were found to 
be developed from similar initials under the same environmental conditions. 
REFERENCE LIST. 
1. Cotton, A. D. : On some Endophytic Algae. Journ. Linn. Soc., vol. xxxvii, 1906, p. 293. 
2. Huber, G. : Contributions a la connaissance des epiphytes et endophytes et leurs affinites. Ann. 
Sci. Nat., ser. 7, Bot., vol. xvi, p. 265. 
3 . Klebs, G. : Die Bedingungen der Fortpflanzung bei einigen Algen und Pilzen. Jena, 1896. 
4. Lang, W. H. : A Theory of Alternation of Generations in Archegoniate Plants based upon 
Ontogeny. New Phytologist, vol. viii, 1909, p. 5. 
5. Livingston, B. E. : On the Nature of the Stimulus which causes Changes of Form in 
Polymorphic Green Algae. Bot. Gaz., vol. xxx, 1900, p. 289. 
The Plate and description of Figures will follow in a subsequent number of The Annals 
of Botany. The delay is in no way due to the author. — Editorial Note. 
