210 



SCIENCE 



[N. S. Vol. XXVII. No. 684 



distinguishable eighteen to twenty months 

 before the time of blossoming. The ovules 

 are formed during tlie late summer and 

 fall months of the year previous to blos- 

 soming. In nearly all cases the ovary is 

 one-chambered, with but one ovule in each 

 chamber. This is orthotropous and pend- 

 ant from the upper part of the cavity. 

 Occasionally two chambers are found with 

 one or more ovules in each. 



A single archesporial cell is differ- 

 entiated, which becomes the spore-mother 

 cell. This, by two successive divisions, 

 gives rise to four megaspores. In most 

 eases the two megaspores toward the 

 chalaza end lie in the long axis of the 

 ovule, while the two toward the micropylar 

 end lie transversely. All four spores 

 germinate, the innermost one giving rise 

 to the embryo-sac, the others breaking 

 down. 



The first divisions of the oospore are 

 transverse and a row of three to four cells 

 is built up before anticlinal walls appear. 



In the development of the endosperm a 

 period of free cell formation is followed by 

 the appearance of cell walls whereby a 

 tissue is built up throughout the embryo- 

 sac. It grows rapidly and soon begins to 

 encroach upon the inner and outer integu- 

 ments and finally begins to push back into 

 the basal tissue of the ovule. 



The antipodal cells give rise to a tissue 

 made up of a considerable number of cells 

 with greatly enlarged nuclei. 



The.proembryo undergoes rapid changes, 

 at first becoming club-shaped and later 

 on pyriform or ovoid. A short suspen- 

 sor made up of several rows of cells is 

 formed. Upon one side of the embryo, 

 near the suspensor, a small depression ap- 

 pears which deepens into a groove. On the 

 axial side of this groove the leaves and 

 plumule are differentiated. The axes of 

 the plumule and the radicle form a some- 



what acute angle with each other, the one 

 being bent back upon the other. 



During the differentiation and develop- 

 ment of these structures, the protocorm has 

 completely devoured the endosperm and 

 all traces of the integuments have disap- 

 peared. The only ovular tissue left is a 

 small remnant on one side of the naked, 

 nearly spherical embryo. 



Regeneration in Root-tips of Vicia and 



Phaseolus: C. H. Shattuck. 



This paper gives the results of the 

 writer's recent experimental work at the 

 University of Chicago. The important 

 points developed by this study are as fol- 

 lows: (1) The lysigenous breaking down 

 of the plerome cells above the point of 

 wounding; (2) the fusion, at certain levels, 

 of young cells from opposite sides of a 

 split root-tip in the region of the perieycle ; 



(3) the disrupting of these tissues at lower 

 levels, thus giving rise to two distinct roots ; 



(4) the complete restoration of the cir- 

 cular form of the root by means of a radial 

 meristem in which the ordinary transverse 

 orientation of the cell plate becomes longi- 

 tudinal; (5) the encircling of stems by a 

 whorl of new roots when spirally cut 

 through the perieycle; (6) that the root 

 orients itself geotropically, not because the 

 vegetative point has reached a particular 

 stage, but always because of the appear- 

 ance of statolithic starch and fails to re- 

 generate if this does not appear. 



Notes on Gymnosporangium macropus: F. 



D. Heald. 



Gymnosporangium macropus has been 

 considered an annual, but the investiga- 

 tions carried on by the author in Ne- 

 braska have shown that two years is re- 

 quired for the "cedar apples" to reach 

 maturity. Young "cedar apples" can be 

 found nearly a month before the rust spots 

 on the apple leaves have matured any 



