NATURAL SCIENCES OF PHILADELPHIA. Ill 



achenia were but the remains of other flowers which had been 

 absorbed by the central and stronger one in an earl}' stage of their 

 existence, and b}- this adnation had become an integral part of the 

 structure of the flower. 



He had now to exhibit to the Academy a small plant of this 

 species, which had grown in a pot in his hot-house during winter, 

 and which was in floAver, and not onl}- exhibited this fact better than 

 the specimens he had brought to the notice of members last 3'ear, 

 but also presented some other very remarkable phenomena. Here 

 was a regular gradation of true horns down to an entire separation 

 from the central achenium, in which case these detached horns bore 

 the usual twin pistils, or rather elongated stigmas. But what was 

 remarkable in this case was that beneath all these normal and 

 abnormal pericarpia some small bulbels issued from the stem, 

 and these also had stigmas more or less perfectly developed. 



The whole plant, he observed, was in many respects a curiosity, 

 which would rival the art-produced Japanese dwarf. Here was a 

 plant a little over an inch in height, which, at the second node above 

 the cotyledons, commenced to produce female flowers. There were 

 no male flowers. Indeed, it was not impaired nutrition which 

 gave it its dwarf character, for the soil in which it was growing 

 was very rich, and the bright green color of the plant was opposed 

 to all idea of starvation. 



Another sug-o-estion occurred to him in connection with the little 

 plant exhibited. The ambrosia was the common rag-weed of our 

 cultivated ground. When such plots of ground were put down 

 into grass, no more of this weed appeared; j'et, though this gronnd 

 remained in sod an unlimited number of 3'ears, when broken up the 

 ambrosia always appeared in immense numbers. Though we know 

 that the seeds of this weed, preserved as ordinary garden-seeds 

 are, will only live a season at best, j^et all farmers and many good 

 botanists believe that the plants spring from seeds of the crop 

 which ripened many years before, and which have retained their 

 vitality through all the period. But if such pigmy plants as these 

 can perfect their seeds, we see at once how hundreds can exist 

 amongst the grass and other vegetation, thus perfecting seeds and 

 perpetuating themselves year after year successively, full}' ac- 

 counting for the appearance of plants on the subsequent breaking 

 up of the sod, without resorting to a mere imaginary theory of 

 wonderful vitality. 



Mr. Gentry directed attention to the fact that Alyssum calyci- 

 num, Lin., a native of Europe, was growing abundantly' on the 

 western side of the Mt. Airy water-works, near the city, where it 

 appears to have permanently established itself. 



1871.] 



