122 BOTANICAL GAZETTE | FEBRUARY 
Reinke (3) treats of the structure of the root tip in later 
stages, but not at the time of the first appearance of the cap. He 
reduces the roots of all phanerogams to one type, that found in 
Helianthus, with separate initials for plerome, periblem, and 
dermatogen, the latter proliferating to form the cap. 
Fleischer (6) describes a mode of cap origin identical with 
Hanstein’s Capsella, but gives no figures. His account derives 
the cap from the cell next to the octants, differing in this respect 
from all other descriptions of Composite embryos. In the 
structure of the older root tip he agrees with Reinke. 
Janczewski (4,5) confines his attention to older roots, and 
distinguishes four types of root-tip structure, one of them being 
the “‘ Helianthus type.” He claims, however, that the cap does 
not arise by the splitting of the dermatogen, but that the inner 
layer of the root cap is a ‘‘calyptrogen,” which later abandons 
its protective function and becomes the epidermis. Later authors 
have assigned various plants to the “Helianthus type,” without 
noticing that their description agreed with Reinke’s account, 
rather than with that of Janczewski. The validity of the Heli- 
anthus type is not to be questioned, for these two views are 
really but two different interpretations put upon the same struc- 
ture, Reinke’s view having been adopted by all the later writers 
as the more natural one. 
Holle (8) claims that the Helianthus type is the character- 
istic one for dicotyledons, and that all other types are mere varia- 
tions. The primary origin of the root cap is not discussed. 
Inthe embryo of Senecio aureus, according to Mottier (20), 
the cell below the octants divides first by one or two transverse 
walls, and the resulting cells divide longitudinally, adding derma- 
togen and periblem to the embryo. The cap is probably formed 
by the next cell below, that is, by the second “ suspensor cell.” 
Maxwell (22), although doing no work upon the Compositae, 
has given us one of the best reviews, in English, of the work of 
these earlier writers. 
Schwere (24) finds that in Taraxacum the first and second 
cells of the suspensor add dermatogen and periblem to the 
