1887.] NATURAL SCIENCES OF PHILADELPHIA. 119 



some cliemical accident than on vital power, that it was doubtful 

 if sugar in any quantity had ever been made from it in China or 

 anywhere else. Certainly the specimens sent by Miss Fielde were 

 of the true sugar cane, as grown by us in the Southern States. 



Floral Calendars. In regard to the times of flowering of plants, 

 Mr. Meehan exhibited blooms of the winter Aconite, Eranthus 

 hyemalis, and the Snowdrop, Galanthus nivalis, which this year 

 were blooming together on the 10th of April. In other seasons the 

 same plants, growing side by side, had given flowers of the winter 

 Aconite, several weeks before the Snowdrop. The explanation was 

 that some plants would start into growth at a lower temperature 

 than others. The Snowdrop would remain at rest under a low 

 temperature quite sufficient to excite the Aconite. In a season 

 when the thermometer remained regularly lower than sufficient to 

 excite growth in the Aconite, the plant remained quiescent until the 

 warmer spring weather brought forward both kinds together. These 

 facts showed that no such a scheme as a floral calendar could be 

 established, as the relative blooming of plants depended on accidents 

 of temperature rather than on any fixed climatal conditions. 



Cortical Peculiarities in the Plum. Some specimens of supposed 

 hybrids between the Peach and the Plum were sent to the Academy 

 for examination. The chief reasons for the belief that they were 

 hybrids were that they were sterile, and seemed in leaf and 

 branches intermediate between the two species. Mr. Meehan 

 observed, that in hybrids between acknowledged species, it did not 

 follow that the characters should be intermediate. Often there 

 would be scarcely any trace of the action of the male parent, while 

 at other times the male would seem to have had a leading influ- 

 ence. But these plum branches showed no trace of any inter- 

 mediate characters, but were purely plum branches, with no sign 

 of the Peach character about them. 



He said he had called the attention of the Academy on several 

 occasions in the past to the fact that the bark of trees did not crack 

 from the mechanical pressure of wood-growth, as so often taught in 

 botanical text-books, but the rifts arose from the peculiar growth of 

 cork cells, and it was the character and general direction of these 

 growths, apparently different in species, that gave the varied char- 

 acters to tree bark, characters that were more or less constant in 

 each species of tree. A tree could in fact be nearly as well 

 known by its bark as by its fruit. The development of the cork 

 cells destroyed the cuticle. In the Cherry and Birch the chief 

 development was in a lateral direction, and hence we could easily 

 strip sections from around branches. In the Abele Poplar the 

 development destroyed the bark to a considerable depth, and in a 

 quadrangular form.' These gradually met at the points and at once 

 formed deep furrows up and down the stem. In the Plane and 

 some other trees, the cork cells worked up and down under thick 

 layers of bark which it threw ofl" in flakes. But the chief distinc- 



