12 
Regarding it as a cotyledon explains the peculiar position of the first 
leaf over the scutellum. Many authors, he says, regard the plumule- 
Sheath as a part of the cotyledon, surely an incorrect idea. Lermer 
and Holzner! in an exhaustive histological treatise on Hordeum vulgare 
describe in detail the different parts of the fruit. They regard the 
scutellum as a shield-like expansion of the hypocotyl, acting as a 
special absorption organ, and the plumule as composed of four leaves 
inelosed in a plumule-sheath, but attempt no interpretation of the 
latter view. 
Bruns’ has investigated the grass embryo chiefly from a systematic 
point of view. He describes and figures a large number of genera of 
each of the tribes. He regards the scutellum as one cotyledon, and 
the epiblast as a second, much reduced on account of the great 
development of the former. He considers it of no consequence from a 
systematic standpoint whether or not the scutellum and the epiblast 
are regarded as two cotyledons, provided it is granted that they 
represent two leaves, as the cotyledons are the first two leaves placed 
together. The plumule-sheath is the thickened first leaf of the plumule 
especially adapted for protecting the young leaves. It has no blade, a 
common characteristic of the lower leaves of grasses. Schlickum, in 
comparing the cotyledons of the monocotyledons, says that when the 
eotyledon has assimilating functions to perform its lamina displays a 
differentiation into a nutrient portion, the haustor, and a conducting 
portion, the conductor. In the grasses the conductor is very rudi- 
mentary or entirely suppressed, while the scutellum is transformed into 
the haustor, which bears no resemblance to a foliage leaf. The epiblast 
is probably an outgrowth of the coleorhiza. When the cotyledon does 
not emerge above the soil its function is to take up, by means of the 
haustor, the nutrient substances present in the endosperm, and to pro- 
tect the rudimentary leaves by the formation of a more or less 
developed cotyledonary sheath. 
Finally, Celakovsky* reviews the work of previous investigators and 
criticises them especially in regard to the homology of the epiblast 
and plumule-sheath. He believes that the true morphological nature 
are joined at the base; where they separate; and whether the plumule- 
MÀ e ZONES CN Sgt n ũà4àéẽk P . 222 RR ur 
Beitrage zur Kenntniss der Gerste. Munchen, 1886. Extract by Brown and 
Morris Chem. Soc. Jour. vol. 57. 1890. 
? Morphologischer und anatomischer Vergleich der Cotyledon und ersten Keim- 
blatter der Keimpflanzen der Monocotyledon. Bibl. botan. Heft. 35. 
4 Uber den Homologien der Grasembryo. Bot. Zeit., Sept. 1897. 
ERU (pete ESTER, EA py 
DES 
