372 



SCIENCE. 



[N. S. Vol. I. No. 14. 



isi for September, 1893, XXVII., 769-781, 

 entitled ' The Philosophy of Flower Sea- 

 sons,' I have just contributed an article to 

 the same journal, Feb., 1895, XXIX., 97- 

 117, giving the results of local observations 

 on the same siibject. After my paper was 

 in tj'pe, I found a short article in Nature, 

 XXVII., 7, by J. E. Taylor, entitled "' The 

 OrigLQ of our Vernal Flora,' which sug- 

 gested some reflections bearing upon the 

 problem. These, with other thoughts re- 

 lating to the subject, were too late to be in- 

 corporated in an article which was already 

 of considerable length. A consideration of 

 these items, however, may not be out of 

 place in connection with an examination of 

 the article by Mr. Harshberger, in Science, 

 Jan. 25, 1895 ; New Series, I., 92-98. 



Commenting upon the fact that it is usual 

 to assign an Arctic origin to our mountain 

 flora, but without giving references, Mr. 

 Taylor says : " Seeing that temperature is 

 so largely influential in. explaining the dis- 

 tribution of flowering plants, it occurs to me 

 that not only may height above the sea- 

 level answer to northern disti-ibution, but 

 seasonal occurrence as well." Briefly, this 

 covers Mr. Harshberger's propositions num- 

 bered 1, 2 and 3 on page 95. 



Mr. Taylor observes that the early flow- 

 eriug plants blossom two or three months 

 earlier in Great Britain than within the 

 polar circle. For example, Chrysosplenium 

 oppositifolium and G. alternijolium bloom ' in 

 March or April ; within the Arctic circle 

 not until June and July, and even so late 

 as August.' This suggests a general re- 

 tardation of flower seasons as we go north- 

 ward, and I have used this assumption as 

 in part explaining the late blooming of some 

 of the luxuriant, highly specialized groups, 

 which MacMillan* calls ' north-bound.' In 

 many of these, flowering is preceded by a 

 long vegetative period. In the northward 

 movement, if the vegetative period remains 



*Higher Seed-Plants of the Minnesota Vallej', 1892. 



of the same length, it seems probable that 

 the flowering would be later in consequence 

 of this period beginning later. 



Mr. Clarke's paper is an elaboration of the 

 idea of the preponderance of the less-special- 

 ized flowers in the earlj' part of the season 

 and of the more highly specialized flowers- 

 in summer and autumn, and I have criti- 

 cised this theory from the standpoint of the 

 local flora of my neighborhood, and have 

 undertaken to account for flower seasons as- 

 a result of the competition of flowers among 

 themselves and in correlation with the 

 flight of the anthophilous insect fauna. 

 The reader is referred to these papers for a 

 more extended discussion of the relations of 

 flower seasons and the specializations of 

 floral structure. 



Mr. Harshberger's observations upon the 

 lull or break in the continuity of the floral 

 procession, which he says at times occurs, 

 is quite interesting. He says : ' ' Such a 

 break seems to occur in the neighborhood 

 of Philadelphia between the twenty-fifth 

 day of May and the tenth or fifteenth day 

 of June, when the first true summer plants 

 appear. Curiously enough, this period cor- 

 responds with the time of the ice saiats in 

 the United States, when there is a possi- 

 bility of frost over a large portion of our 

 continental area." 



There is a lull, however, Avhich, at least as 

 regards the entomophilous flora, takes place, 

 not ' at times,' but regularlj'. The fi*ost 

 may, indeed, in manj'' cases have a very 

 definite effect in preventing plants from ad- 

 vancing into the spring months, probably 

 indirectly, however, through its influence 

 upon the vegetative state which precedes- 

 flowering. The time of the ice saints, ac- 

 cording to Harrington,* is from May 19th 

 to 24th, while the floral dej^ression is later. 



In the neighborhood of Carlinville, 111., 

 the entomophilous flora shows a slight de- 



*Harper's Sronthjy, LXXXVIII., 878. 1894. Ar- 

 ticle cited by Harshberger. 



