LLL LL 
wa eee canna na aR 
An occurrence of glands in the embryo of Zea Mays 
a CHARLES STUART GAGER 
The embryo of the grasses is an ancient battle-ground. Con- 
troversies over the homology of its various parts, and over their 
several functions, have been waged almost continually since the last’ 
half of the seventeenth century, when Malpighi® first described its 
anatomy. Its study formed part of the basis on which Schleiden?® 
and Schacht’ concluded that plant embryos originate in the end of 
the pollen-tube, while the embryo-sac serves only to protect and 
nourish them. By its study, in part, Mirbel and Spach,’ and 
Brongniart ' were led, on the other hand, to a diametrically opposite 
conclusion, namely, that the embryo originates in the embryo-sac, 
and that only after fecundation by the pollen. 
The battle has waged fiercely over the indentification of 
the true ‘cotyledon. The term scutellum (little shield), merely 
descriptive, harks back to Gaertner,’ in 1788. His studies on the 
fruits and seeds of plants were considerably colored by his inves- 
tigations of the eggs of animals, and he interpreted the shield- 
shaped organ in the grass embryo to be analogous to the vitellus, 
or nutritive part, of the animal egg. Hence he referred to it as 
“< attellus scutelliformis,” or, briefly, scutellum. That he recognized 
it as really homologous with the cotyledon in other families is evi- 
denced by the term “‘scutel/um cotyledoneum”’ which he also 
employed. * 
The literature shows some diversity in the significance with 
which the term scutellum is employed. Most authors use it, as 
Gaertner originally did, to apply to the entire organ, but at times 
its meaning has been narrowed} to the outer layer of cells, or epi- 
thelium of the shield. There seems to be little warrant and small 
gain in this latter restriction of it use, and the practice should be 
discouraged. he ee 
~~ * + Singularem hanc Vitelli speciem, proprio Scutelli cotyledonei nomine distingui- 
mus,’? Gaertner ® (page cxlix). 
+ Brown and Herron. Jour. 
Chem. Soc. Lond. Trans. 35 : 623. 1879. 
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