Feb., 1908.] 
Embryology of Oxalis corniculata. 
2 61 
THE EMBRYOLOGY OF OXALIS CORNICULATA * 
Howard S. Hammond. 
Oxalis corniculata might be called a sub-tropical plant 
although it is frequently found growing in ballast about the 
Eastern seaport towns of the United States and becomes quite 
abundant in Texas. In tropical America it is quite common and 
is also reported as occurring in the tropical regions of the Old 
World. It has been reported as far north as Ontario. Fre¬ 
quently it is found growing on the ground in greenhouses where 
it blooms profusely throughout the year. It was under these 
last named conditions that the writer secured the material with 
which he worked. The material was collected throughout the 
Spring of 1906 and the Fall and Winter of 1906-1907. The 
usual methods of killing and imbedding were used. The sections 
were cut 8 mic. thick and stained on the slide. Delafield’s 
Haemotoxylin proved the most satisfactory stain. To Prof. 
John H. Schaffner under whose direction this study was begun 
and to Prof. Robert F. Griggs under whom the study was com¬ 
pleted I desire to express my sincere thanks for their kind 
assistance and suggestions. 
MEGASPORES AND EMBRYO SAC. 
The nueellus consists of a single axial row of cells invested by 
the epidermis (Fig. 1). The uppermost cell of the axial row is 
the archesporium which, thus appearing very early, increases to 
two or three times its original size. It does not give rise to 
parietal tissue but undergoes directly the Reduction Division 
which was not observed (Fig. 2). The lowest of the three or 
four megaspores thus formed becomes the functional one, and 
rapidly enlarges at the expense of the potential ones above, giv¬ 
ing rise to the two (Fig. 3), four (Fig. 4), and eight (Fig. 6), 
celled embryo sacs in the usual manner. Before the two celled 
embryo sac is formed the surrounding epidermis which functions 
as tapetum, has begun to disintegrate and the sac is subsequently 
enclosed simply by the integuments. The embryo sac develops 
very rapidly and is nearly straight although the ovule is anatro- 
pous. The antipodals are small, stain darker than the polar 
nuclei or the unfertilized egg, and begin to disintegrate at the 
time of the conjugation of the polar nuclei (Fig. 6), sometimes 
disappearing before fertilization in case that is delayed till after 
the polar nuclei have fused (Fig. 5). The svnergids stain dark, 
are rather large, and also disintegrate early, one of them being 
destroyed by the entrance of the pollen tube (Fig. 6). 
ENDOSPERM AND EMBRYO. 
Connecting the endosperm cells are radiations, as has been 
frequently observed in many plants, but these are not kino- 
* Contributions from the Botanical Laboratory of the Ohio State University, XXXIII. 
