392 PROCEEDINGS OF THE ACADEMY OF [1888. 



was only in seasons when the stamens and pistils matured simulta- 

 neously, that large crops of nuts followed. I had overlooked at that 

 time, the fact that something similar had been placed on record be- 

 fore. In the Transactions of the Horticultural Society of London, 

 vol. V, 1824, is a pajjer by Rev. George Swayne, showing that the 

 filbert crop in Kent fails two years out of five ; that some seasons 

 the catkins mature before the female flowers open, and at others not 

 till afterwards, and that failure to produce a crop results from the 

 absence of pollen at the period when the female flower is in receptive 

 condition. All I can, therefore, claim as original is the formula that 

 varying measures of heat influence variously the separate sexes, — 

 the smaller measure influencing the male, while the female still con- 

 tinues to rest. 



Since my observations were made on the hazel, I have extended 

 them to other plants. It has long been known that in many of the 

 Central States coniferous trees that produce seeds abundantly farther 

 north, rarely have one perfect seed in those regions. I know this is 

 so in the vicinity of Philadelphia. The Norway spruce may pro- 

 duce cones by the cart-load, with not an ounce of seed in the lot. 

 Since the observations above cited I find that the male flowers ma- 

 ture long before the female, and affords a satisfactory reason for the 

 failure. Further north, where winter does not coquette with spring 

 as here, they remain in rest equally, and advance together. In their 

 gregarious, forest condition, no doubt the extent of surface conduces 

 to an equilibrial condition of climate not surrounding isolated trees 

 in a cultivated state. 



In brief, I may enumerate a number of coniferse, alders, Avalnuts, 

 chestnuts, oaks, hickories and the hazel-nut as among those that I 

 carefully watched for the few years past, noting a wide range of 

 difference each season between the times of maturing of the male 

 and female flowers. The season of 1887-8, I noticed was favorable 

 to a simultaneous maturity of the sexes. I exhibited specimens in 

 the spring of 1888, to the Botanical Section of the Academy, and 

 had no difficulty in predicating on the fact of simultaneity an 

 abundant harvest of nuts, which has been fully realized. I have 

 since been observing the working of this principle in elms and 

 maples — hermaphrodite plants ; the species under observation being 

 Ulnius americana, and J.cer dasycarpum. The trees of the former 

 were comparatively young, but had flowered the first three years 

 without perfecting more than a seed here and there. I had no 



