2u2 



SCIENCE. 



[N. S. Vol. XXIII. No. 580. 



abnormal leaves to the normal pitchers of 

 Sarracenia and Nepenthes, and to the pel- 

 tate leaves of many other species, was re- 

 called, and it was shown that the relation 

 between the pitcher and the peltate leaf 

 rests upon the ratio between radial and 

 tangential growth of the leaf tissue, and 

 that this ratio fluctuates about a definite 

 mean value for a particular position in 

 any given species, whether the development 

 occurs in a complete circle or in a broken 

 circle. This ratio determines the narrow- 

 ness of the ascidium, as well as many other 

 details of leaf form, such as plications, 

 curled and upturned edges, etc. It was 

 observed that this ratio was apparently 

 greater in the ascidia than in a normal leaf 

 and it was suggested that this appearance 

 is due to the development of a sector of 

 leaf tissue in the place of the normal sinus, 

 and that this sector must be taken into 

 account when comparing the ascidium with 

 the normal leaf. Exception was taken to 

 the frequently expressed idea of fusion, the 

 essential feature of the ascidium being de- 

 scribed as due to the retention of a capacity 

 for further radial development by certain 

 cells in the median dorsal line, which cells 

 normally lose this capacity at a very early 

 stage of development. It was noted that 

 the ascidia could be referred to two types, 

 the more common form involving the basal 

 margin of the leaf, the other being located 

 within the leaf and leaving the basal mar- 

 gin normal. The former was called a 

 seamless ascidium. It comprised a little 

 over 50 per cent, of the eases, and the 

 seamed ascidia were found in about 47 per 

 cent. Several peculiar combinations of the 

 two types were noted. The stalk of the 

 seamless ascidium differs from a normal 

 petiolule in that it is cylindrical and con- 

 tains a single concentric bundle, the nor- 

 mal stalk containing, in addition to this, 

 two small collateral bundles running be- 

 neath two ridges which are continuous with 



the leaf margins. A strongly marked ' 

 periodicity in the position of the ascidia 

 in the leaf was found to agree closely with i 

 that found by Miss Tammes for their oc- 

 currence on the branches of Tilia, which ; 

 fact suggests the morphological similarity 1 

 of leaf and branch. This period for j 

 Fraxinus was as follows: Of 103 ascidia j 

 96 were on terminal leaflets, five on the ulti- i 

 mate pair of lateral leaflets and two on the I 

 penultimate pair. This occurrence of as- j 

 eidia on the terminal leaflets agrees with : 

 recorded observations on other species | 

 having polyphyll leaves and this fact was j 

 adduced as further evidence of ortho- 

 genesis. When the two leaves at any node 

 spi-ead laterally, they show a strong 

 tendency to be symmetrical with regard to ; 

 the occurrence of ascidia, but when they 1 

 spread in a vertical plane, only the lower . 

 leaf bears an ascidium. The extreme local- ] 

 ization of ascidia-bearing ash trees was pre- 

 sented as evidence of their recent origin at 

 this particular spot, and the fact that a ; 

 large number of individuals of various i 

 ages possess this structure was held to be 

 strong "evidence in favor of their inherit- 

 ability, but both the origin and inheritance ] 

 must await demonstration by pedigree- ', 

 culture. j 

 Phytogeography of Florida: P. H. Kolfs. 

 (I.) A discussion of the general con- 

 formation of Peninsular Florida giving a 

 general outline of the topographic regions. j 

 (II.) The distribution of pine woods. j 

 Plants associated with this formation. ' 

 (III.) The scrub formation and its plant 

 association. (IV.) The mangrove forma- i 

 tion and its associates. i 



The Florida Strand: P. H. Rolfs. , 



A discussion of the Florida strand show- ' 



ing the principal plants with effect of loca- i 

 tion on various species. 



The Everglades: P. H. Rolfs. i 

 A general description of the everglades 



