106 BOTANICAL GAZETTE 
indicates that the walls in question were originally oblique or els 
became so by unequal growth in different parts of the embryo (fi 
36). The dermatogen usually forms first in the terminal segmen 
To distinguish the middle from the terminal segment soon becomes 
difficult matter, but from the position of the concavity in which 
stem apex is developed, it is safe to say that the apex arises fi 
Alisma. The middle segment also gives rise to the root-tip, hy 
cotyl, and part of the suspensor. A short time before the differen 
tion of the stem tip in the lateral depression, the region adjoining 
outside of the area where the stem tip is to appear grows upward in 
a ridge of tissue, which in the mature embryo encloses the growin 
point completely. If the figure of the embryo of Guzmannia, ¢ 
shown by Witrmack in Engler and Prantl’s Natiirlichen Pjlan: 
jamilien be compared with that of 7. usneoides (fig. 4o), the 
blance will at once be apparent. It will be noticed that what I 
called cotyledon in Tillandsia is called scutellum in Guzmam 
the term cotyledon! being reserved by WrrrMackx for the small 0 
growth labeled c, near the stem apex. It is probable that the a 
in thus naming the two organs scutellum and cotyledon only wishes 
to emphasize the difference in function, one as an organ of absorp 
tion, the other as a rudimentary leaf, at the same time recogn 
the two as homologous with the cotyledons of the dicotyledo 
From a study of the seed germination of 7. usneoides, however, 
will be seen that it is extremely doubtful if the organ named cotyle 
in Guzmannia is really such. Further discussion of this point, ht 
ever, will be postponed till seed germination is considered. 
When the embryo of Tillandsia is about three-fourths g 
there occurs a degradation of certain cortical cells of either the | 
or the end of the hypocotyl nearest the root-tip. The cells in qt 
show at first a contracted protoplast, with incapacity to stain deep!y 
and by the time the embryo has reached its full size almost a €0 m 
absence of cell contents (fig. 42). This phenomenon undou 
stands in intimate relation with the complete atrophy of me 
obtains in the mature plant. ee 
‘The index letter ¢ in the description of jig. 19, G of the Bromeliaceae 
found through correspondence to indicate cotyledon. a 
