344 PROCEEDINGS OP THE ACADEMY OP [1886. 



On the Interdependence of Plants. Mr. Thomas Meehan called 

 attention to the well-known fact in geographical botanj', that 

 species of plants which once had evidently a wide dispersion now 

 existed only as separate colonies often of a few plants only, the 

 intermediates between these widely separated colonies having 

 evidently disappeared. The cause of these disappearances had 

 not been definitely determined. It was found that the still exist- 

 ing individuals were evidently in good health ; they flowered 

 freel}-, and perfected seeds, but still the plants did not spread. 

 He gave a number of illustrations within his own observation of 

 a few rare plants that had maintained their existence for over a 

 quarter of a century, with about the same number of individuals 

 now as at the beginning of the term. As the seeding was regular 

 and perfect, why was dispersion arrested ? There could be but 

 one answer. Something prevented the germination of the seeds, 

 or of subsequent growth after germination. No doubt there may 

 be other causes, but this one must have a leading influence. 



It then becomes an interesting branch of study to inquire why 

 these seeds do not germinate, and thus aid the plant to recover 

 the ground lost through destructive agencies ? 



An observation extending over about six 3'ears led him to con- 

 clude that there was much in the interdependence of plants. What- 

 ever afi'ected the existence of individuals of one species might 

 lead to the extermination of numerous others, and the successful 

 endeavor of one to establish itself in one locality gave the neces- 

 sary opportunity to follow and sustain themselves. This obser- 

 vation was as follows : A wood, chiefly of chestnut and oak, of 

 about an acre in extent, was turned into a picnic ground a place 

 for summer pleasure parties. All the shrubby undergrowth was 

 cut away. The plants which might have grown up, were kept 

 tolerably well trodden down by the numerous visitors to the 

 wood, except one solitary blackberry plant (Bubus villosus), 

 which, being thorn}', led to its avoidance by human feet. After 

 the second summer, some change in railroad arrangements led to 

 the abandonment of the wood for picnic purposes, and plants had 

 a chance to grow up again without disturbance from human 

 beings. The blackberry plant, by the aid of its creeping roots 

 now forms a thicket of about thirty feet in diameter. The follow- 

 ing list of plants growing among the blackberries, that were not 

 found in any part of the wood, except the last two, which were 

 in small quantities here and there, was made in October of this 

 year : 



Eupatorium perfoliatum^ Bubus occidentalis, Liriodendron 

 tulipiferum, Cornus alternifolia, Smilacina racemosa, Ambrosia 

 artemisisefoUa, Laurus sassafras, Polygonum Persicaria, Achillea 

 millefolium, Solidago canadensis, Mulgedium acuminatum, Bidens 

 frondosa, Silene verticillata, Fragaria virginiana, Aster longi- 

 folia, Eupatorium album, Circsea lutetiana, Geranium maculatum, 



