288 PROCEEDINGS OF THE ACADEMY OF [1892. 



THE ATJTOSPORADIC SEEDS OF OXALIS STRICTA. 

 By Ernest Walker. 



The effective metliod this plant has of scattering its mature seeds, 

 in which it proves to be a decided "touch-me-not" seems hitherto 

 to have escai^ed observation. In Gray's Manual, and other like 

 works, the seeds are spoken of as having a " loose and separating" 

 coat, but the part this envelope plays in dehiscence and in the dis- 

 tribution of the species is not mentioned. 



In May, 1891, I made some careful observations, and the follow- 

 ing memoranda: — 



As the seeds of Oxalis stricta L. attain maturity, the erect loculi- 

 cidal capsule becomes flaccid. In this condition the least distur- 

 bance, as the touch of the hand or shaking by the wind, causes 

 the seeds to be expelled with considerable force, and thrown two 

 or three feet. Sitting for a few minutes by a plant, the tick of the 

 seeds as they were continually projected could be distinctly heard. To 

 place a capsule in the palm of the hand, and press it, suggested the 

 bursting of pop-corn. 



The shooting of the seed was done so quickly that it was some 

 time before I could make out the manner in which it was j.ccom- 

 plished. 



The active agent is the outer coat of the seed. This consists of 

 a translucent, shining, membraneous envelope stretched tightly over 

 the seed. When it bursts, it suddenly and elastically turns inside- 

 out ; after which it becomes flaccid. 



This coat is thicker in a line along the ventral margin of the pen- 

 dulous seed, or along the edge which is next the axis of the cap- 

 sule. The rupture is naturally along the opposite edge. Doubling 

 back against the axis of the upright capsule gives this membra- 

 neous coat, or spermoderm the power to project the seed. 



Placing some of the seeds under a lens and puncturing the coat 

 with a needle the rupture was found to occur at other parts than the 

 margin, or at any point the coat might be pricked. In this instance 

 the envelope not having a "back-stop" was often thrown farther 

 than the seed. 



When in the capsule the position of the seeds is such as to throw 

 them not only outward but slightly upward. They are cast farther 

 than if projected horizontally. Some seeds were found as far as 

 three feet from the capsule from wliich they were thrown. 



