OCTOBEB i, 1907] 



SCIENCE 



447 



species, it resembles P. nuptialisj Gerst., from 

 Texas, and P. picta, Hagen, from Smyrna ; but 

 it is closer to the latter. In nuptialis the 

 inner edge of the apical black area is straight, 

 but in picta it is zigzag; in the fossil arctii- 

 formis it is as in picta. 



One of the new plants obtained this year in 

 the Florissant Miocene is of interest in the 

 same connection. It is Heyderia color adensis 

 sp. nov., an incense cedar very closely allied 

 to the living S. decurrens (Torrey) K. Koch, 

 of California. The larger leaves are about 

 5^ mm. long, perhaps less acutely pointed than 

 in the living plant, but in arrangement and 

 general structure quite the same. I follow Dr. 

 ]Sr. L. Britton in separating Heyderia from the 

 Lihocedrus of the southern hemisphere; the 

 genus contains two living species, one in Cali- 

 fornia, the other Asiatic. Our fossil agrees 

 very closely with a specimen in the herbarium 

 of the New York Botanical Garden which was 

 collected by Torrey in 1865 in the grove of 

 Sequoia gigantea in California. As showing 

 the persistence of a " plant association," it is 

 interesting to note that the fossil species also 

 grew by or under Sequoia trees, as is proved 

 by a fragment of Sequoia haydeni on the same 

 piece of shale, touching the Heyderia. 

 Sequoia haydeni, the Florissant redwood, is the 

 Hypnum haydeni of Lesquereux, a fragment of 

 it having been originally described as a moss ! 

 t. d. a. cockerell 



Univeesitt of Colorado, 

 botodee, coloeado, 

 September 1, 1907 



CENSUS OF POUR SQUARE FEET 



The approximate numbers of the fruits and 

 seeds, the insects and other invertebrates pres- 

 ent on a given area are data for which the 

 student of economic problems has frequent 

 need. It is important, therefore, to have a 

 more accurate conception of the abundance of 

 these items than is derivable from offhand 

 estimates. The present paper is offered as a 

 contribution to the knowledge of this subject, 

 with the explanation that the results herein 

 detailed are not held applicable to any classes 

 of surface other than those examined, nor to 

 any region but that of Washington, where the 



collections were made. However, it is prob- 

 able they safely may be used as a basis for 

 reasonable analogies with respect to other 

 localities. 



Pausing to note only that the investigation 

 was undertaken primarily because of its rela- 

 tion to the study of bird food, the method 

 used was as follows: areas, two by two feet, 

 of forest floor and of grassy meadow, were 

 examined in November and March, respect- 

 ively. Everything on the surface of these 

 plots and the groimd itself, to the depth a bird 

 easily can scratch, was removed and all plant 

 and animal objects of classes known to be 

 used as food by birds were counted. The fol- 

 lowing were obtained from the four square 

 feet in the woods : Coleoptera 12, Hemiptera 

 Y, Hymenoptera 8, spiders 11, other Arthropods 

 26, Annelids 9, Gasteropods 11, cocoons and 

 insect eggs 27, or altogether 112 animal items ; 

 in addition there were 194 seeds and fruits. 

 Assuming, as we may in perfect justice, that 

 the plot in question was in no way exceptional, 

 the analysis indicates that on the average there 

 are present on each acre of forest floor in this 

 locality 1,216,880 animals of the kinds above 

 specified and 2,107,810 fruits and seeds. 



Prom the four square feet of meadow there 

 were collected: Coleoptera 61, Hemiptera 20, 

 Hymenoptera 940, spiders 53, other Arthropods 

 127, Annelids 3.3, Gasteropods 20, cocoons and 

 eggs 20, or altogether 1,254 animal objects; 

 there were also 3,113 seeds. The averages per 

 acre for meadows, therefore, are : Animals, 

 13,654,710, and seeds, 33,822,745. On first 

 thought these estimates seem incredible. 

 Hence in order to show that they are the 

 result of the summing up of numbers, individ- 

 ually so small, that no one would question 

 them, I present the following complete lists* 

 of the living invertebrates and seeds from 

 each area. 



WOODS: Invebtebrates : Ohilopoda 7; Oligo- 

 chwta 9; Thysanura {including 1 Japyx sp.) 15; 

 Eomoptera (Crypona sp.) 2; Heteroptera [Euschis- 

 ius fissilis 2, E. tristigmus 1, C'ryphula parallelo- 

 gramma 1, Bhyparochromus n. sp. 1) 5; Coleop- 



' For the greater part of the identifications of 

 insects the writer is indebted to Messrs. E. A. 

 Schwarz, 0. N. Heidemann and Nathan Banks. 



