648 SUMMARY OF CURRENT RESEARCHES RELATING TO 



dinal section. The nucellus is formed only in the lateral, not in the 

 terminal corners. The two integuments are formed at the same time 

 on one side only around and not out of it, appearing first at the apical 

 edge of the longitudinal section, and growing also more rapidly here 

 than at the parts nearest to the base of the ovary. The inner integu- 

 ment is clearly formed before the outer one. Both are developed out 

 of the dermatogen, while in other genera it is only the inner one that 

 has this origin. 



In the formation of tbe integuments an elongation of two cells in 

 the case of the outer, of three in the case of the inner integument 

 takes place on the dorsal side, their cells being separated from one 

 another by a single cell. The elongation takes place in two slightly 

 different directions. The outer integument is then formed on the 

 dorsal side by the growth of the apical edge of the two cells, on the 

 ventral side by periclinal and anticlinal divisions of originally at most 

 five cells. The inner integument is formed on both sides out of three 

 cells, the central one of which usually divides periclinally, the two 

 outer ones by oblique walls. 



The thickening of the outer integument takes place by divisions 

 parallel to the longitudinal axis in those cells which form at the time 

 its innermost layer ; the inner integument is formed also in a similar 

 way, and becomes considerably thicker than the outer one. The 

 cells of the innermost layer of the inner integument subsequently 

 elongate in a direction vertical to the longitudinal axis. Special 

 divisions take place in certain cells on the ventral side in connection 

 with the curvature of the embryo-sac. The ovule of Primula is not 

 strictly anatropous, but somewhat between the anatropous and 

 campylotropous form. 



The origin of the formation of the nucellus consists in three hypo- 

 dermal cells of the outermost layer of endoblem raising up the four or 

 five dermatogen cells which lie above them, and giving rise to anticlinal 

 divisions. The centre one of these three cells increases much more 

 rapidly, forcing aside the other ones, which are completely resorbed in 

 the epidermis. In the mother-cell of the embryo-sac arise two and sub- 

 sequently two more transverse walls of considerable thickness and great 

 refrangibility. The lowermost of the four daughter-cells compresses 

 the three others which lie above it, until they finally constitute only a 

 strongly refrangible cap upon the mature embryo-sac. The embryo- 

 sac is fusiform and somewhat crescent-shaped ; it contains two 

 synergidae, an ovum-cell or oosphere, a small " vegetative " nucleus, 

 and three antipodals. 



The funiculus is formed out of the original ovular protuberance ; 

 its endoblem is differentiated into periblem and plerome. The latter 

 developes into a vascular bundle without xylem, composed only of 

 cambiform, which ends directly at the embryo-sac. The periblem is 

 at first composed of a single layer of elongated cells, later of two 

 layers, and finally of large cells destitute of protoplasm. 



Homology of the Ovule.* — L. Celakovsky gives a very minute 

 description of a case of phyllody of the ovules of the columbine ; 

 * Bot. Centralbl., x. (1882) pp. 331-42 ; 372-82 (1 pi.). 



