812 
Compton . — An Anatomical Study of 
possess it there is absolutely nothing to indicate that tricotyly is derived 
from dicotyly by splitting. 
Hemitetracotyl D. There were three cotyledons, one of them being 
split about half-way. The root and hypocotyl were triarch throughout, 
the double bundle supplying the split cotyledon not dividing till after it 
entered the lamina. There were three leaves at the first epicotyledonary node. 
Tetracotyl E. The root was diarch, with two lateral phloems. A third 
protoxylem appeared laterally about a quarter up the hypocotyl, this 
dividing the adjoining phloem into two equal halves ; about half-way up 
the hypocotyl another protoxylem arose de novo on the opposite side of 
the original xylem-plate, this dividing the other phloem. A tetrarch root- 
structure was thus produced, and the upper half of the hypocotyl had 
a symmetrical structure, each xylem-pole producing a double bundle which 
supplied one of the four cotyledons. 
The majority of the tetracotyls examined had diarch roots, but there 
was much variety in the level at which the new protoxylems were added. 
In one case the stele did not become triarch till three-quarters, and tetrarch 
till seven-eighths up the hypocotyl. It was general to find one of the new 
protoxylems appearing at a lower level than the other, though no more 
than a quarter of the hypocotyl separated them in any case. One seedling 
was seen which possessed a triarch root, and no instance of tetrarchy 
occurred in the root. 
Tetracotyls have four leaves in their first epicotyledonary whorl. 
The most striking feature in the schizocotyls of Phacelia is the fact 
that the vascular strands do not split to correspond with the split of the 
cotyledons. In all cases (except two, where the division occurred in the 
lamina) the number of xylem bundles is increased by the addition of new 
ones, not by the division of old. On tracing the strands from above down- 
wards, we may say that in these cases the traces of certain cotyledons or 
half-cotyledons do not contribute to the structure of the root, but die out in 
the hypocotyl. This is the characteristic of ‘ subsidiary cotyledons ’ — 
a category of plant-members which apparently cannot be maintained. 
Other Species with Diarch Dicotyls. 
Antirrhinum majus (Scrophulariaceae). 
ScROPHULARlA NODOSA (Scrophulariaceae). 
Amaranthus SPECIOSUS (Amarantaceae). 
, Clarkia pulchella (Onagraceae). 
Papaver rhoeas (Double and Shirley) (Papaveraceae). 
Seeds of schizocotylous races of the first four species were received 
from Professor de Vries : 1 the Papaver material was derived from trades- 
1 de Vries (’ll), pp. 429, 432, &c. 
