1893.] NATURAL SCIENCES OF PHILADELPHIA. 289 



CONTRIBUTIONS TO THE LIFE HISTORIES OF PLANTS, NO. 9. 



BY THOMAS MEEHAK. 



POPULUS TREMULOIDES. — A MONCECIOUS CASE. 



Noting on a young tree of Populus tremuloides on my grounds, 

 which I had supposed to be a male, that a few of the catkins were 

 still green when the most of them were faded, I was led to exam- 

 ine and found they were female. There were thirteen of these 

 female catkins, and one hundred and fifty-one males. Seven of the 

 pistillate aments had about one-third of the scales bearing stamens 

 only, and about two-thirds with pistils only. Two were solidly pis- 

 tillate with but a few stamen-bearing scales at the base. One had 

 staminate scales for about one-third of its length from the base, the 

 remaining two-thirds of the catkin being uniformly pistillate; while 

 one was almost wholly male, there being but three female scales 

 among the whole number. Two were purely pistillate, no trace of 

 a staminate scale could be observed. The tree was seven years old, 

 and growing freely, having made a growth of about three feet each 

 year, for three years past. Some of these bisexual aments will be 

 preserved in the herbarium of the Academy of Natural Sciences of 

 Philadelphia. Bisexual scales were sought for but did not appear 

 to exist. 



Changes of sexual characters in dioecious plants are not uncom- 

 mon, but have probably not been recorded before in connection 

 with Salicaceous plants. The author has a large number of species 

 of willow growing on his grounds. All these were subsequently 

 examined carefully, but no similar case of sexual change was found 

 among them. 



Extra-Axillary Branching in Mertensia maritima. 



Of this plant, as " Steenhammera maritima (R. 1 )," Babington, 

 in his " Manual of the British Flora," remarks that in habit, " it is 

 sui-generis." I know of no attempt to explain the singularity. A 



*It may have been noted that in these biological papers, the name of the 

 author of the species is seldom quoted. This omission is intentional though con- 

 trary to modern custom. In a treatise on systematic botany, such quotations are 

 certainly in full place. But in public addresses or in everyday language, no one 

 would think for a moment of repeating an author's name every time a plant was 

 referred to, and there seems no reason why a scientific treatise when written in a 

 conversational way, should not follow conversational rules. 



