1g11] CURRENT LITERATURE 487 
the fungus must remain in that genus. Several other species of Karschia are 
numbered among about 400 fungi that grow on lichen thalli, and a study of 
each of these would be of special interest and value. 
The author states that his study of these two fungi proves that there can 
be no sharp separation of the many fungi known to grow on lichens into para- 
sites, parasymbionts, and saprophytes, since a single species may show all 
three conditions at various times in its life history. He thinks that further 
studies would demonstrate that most of the fungi found growing on lichens 
are not purely parasitic, but parasymbiotic and often saprophytic as well. In 
this he is probably correct, and further research along this line would add 
much to our knowledge of the biological relations of these fungi. The c con- 
demarkation between lichens and other fungi. This is true, but a consider- 
able number of botanists have already concluded that the oa distinction 
between lichens and other fungi should not serve longer to maintain the 
lichens as a distinct group in any general classification of plants. 
Some other fungi growing on lichens were examined briefly, without add- 
ing materially to the important results secured in the study of the two species 
considered above.—Bruce FINK. 
Evolution of vascular structures.—In a bulky memoir of 325 pages, CHAU- 
VEAUD*® expounds his view of the evolution of vascular bundles as they are 
found in different groups of plants. He finds himself in disagreement with 
the current notion of the stele as a morphological concept of first importance, 
and returns to the earlier view of a vascular bundle as the unit. With him, 
in fact, a vascular bundle is either a xylem or a phloem group, and these are 
arranged according to one of six “dispositions”: (1) centric, corresponding 
to protostele; (2) excentric, with the xylem group more or less flattened; (3) 
alternate, represented by a root with diarch structure; (4) intermediate, as 
seen in the hypocotyl of some plants; (5) su , a circular row of co- 
lateral bundles; and (6) peripheral, FE by amiphivasal bundles such 
as are seen in monocotyledonous stems. Thus what most writers call a pro- 
tostele is by CHAUVEAUD, as well as earlier writers, regarded as the most 
primitive condition; the alternate arrangement of xylem and phloem exhibited 
by all roots is the next main step in evolution; and from this root structure 
are to be derived the conditions seen in the stems of gymnosperms and angio- 
sperms. It will be seen that this mode of derivation lays a heavy responsi- 
bility on the hypocotyl, for this transitional region is considered to reveal the 
stages in evolution leading to the stem structure of all the higher plants. 
One must swear entire allegiance to the recapitulation theory when adopting 
this scheme, although certain difficulties appear, for instance, in connection 
2s CHAUVEAUD, G., L’appareil conducteur des aon vasculaires e 
principales de son évolution. Ann. Sci. Nat. Bot. IX. 13: 113-438. rig or) Igtl. 
