December 1, 1905.] 



SCIENCE. 



711 



globose and dark red, and in the other ob- 

 conical and yellow and brown, in maturing, 

 respectively. The hybrid character of some 

 individuals must be admitted in theory, bn' 

 the presence of the two types associated in the 

 same habitat is beyond doubt. 



Again, to cite a striking, if sweeping, illus- 

 tration, it is to be properly appreciated that 

 all the species of the fleshy Euphorbiaceas 

 are confined to one grand region, and all the 

 analogous species of the Cactacese to another. 

 The species composing a genus raay not be 

 exactly coextensive, but the ranges of many 

 species may and often do overlap, and are to 

 this extent coincident. 



Among the violets, the old species, of Gray's 

 ' Manual,' Viola palmata, a few years ago was 

 made to comprehend a number of ' varieties ' 

 then so called. These have now been showii 

 to be a number of distinct but closely related 

 species, some of which, at any rate, exist side 

 by side in the same habitats and have the same 

 or similar ranges. The same may be said of 

 the certain yellow, stemmed violets, and of the 

 white violets, Y. lanceolata and primulce folia. 



Two species of Drosera, rotundifolia and 

 longifolia, are constantly found together and 

 are usually expected to be so found by every 

 collector. Two other species are often asso- 

 ciated with them, though not always. 



(Enothera hiennis and 0. Oakesiana grow 

 together in the same habitat. So also Asclepias 

 incarnata and piilchra, two species of the milk- 

 weed which are not readily recognized by the 

 tyro, but are yet perfectly distinct, grow con- 

 stantly associated in the same swamp. 



Bhodiola integrifolia is distributed from 

 Colorado to Alaska. In Colorado B. poly- 

 gama, closely related to it, is found with it in 

 the same habitat. The two are not separated 

 by any geographical barrier. 



Of the Potentilla quite a number of species 

 are very often associated, especially those of 

 the nivea, gracilis and ruhicaulis groups. 

 Three or four of the species may usually be 

 found growing in the same patch of an area 

 not larger than a good-sized room. Of the 

 sedges, many species, often closely related, are 

 to be found in the same bog. 



The hammocks of Florida are particularly 

 interesting in this connection because of the 

 great number of species to be found in 

 restricted habitats. Two species of white- 

 flowered Lantana, odorata and involucrata, 

 are always or nearly always found together, 

 and this applies to the two yellow-flowered 

 kinds, depressa and ovatifolia.- The two live- 

 oaks, Quercus geminata and Virginiana, are 

 in the same case. Catopsis nutans and Ber- 

 teroniana grow intermingled on the same tree, 

 and the same may be said of many other 

 epiphytic species, including Tillandsias, Epi- 

 dendrons and other orchids. It is worthy of 

 remark that just at the places where the 

 struggle for existence may be presumed to be 

 the most intense between the individuals of 

 the vegetation there also do we find many 

 examples of the same association of closely 

 related species. 



Among the ferns, examples are numerous, 

 notably so again in the case of the tropical 

 epiphytic filmy fern, Elaphoglossums and 

 Polypodiums, which grow intermingled, as 

 every one can testify who has examined her- 

 barium specimens which are often composed 

 of two closely related species and therefore 

 not discerned as. such by the collector. In 

 Jamaica there are a half-dozen species of tree- 

 ferns which are endemic to the island and are 

 practically always intermingled ! Of northern 

 edaphic species Botrichium oUiquum and 

 dissectum are always expected to be found 

 growing together, and the same may be said 

 also of B. neglectum and lanceolatum. Dry- 

 opteris Goldieanum, though more restricted 

 in its choice of habitat than D. marginale, is 

 often found with it. 



Examples among the mosses and liverworts 

 are abundant. Orthotrichum Brownii, Ohio- 

 ense and hrachytrichitm may not infrequently 

 be found mixed together, and even three other 

 species of this genus may be associated with 

 them, all growing on trees. The rocks support, 

 for example, Dicranum longifolium and 

 viridis, often components of the same tuft, 

 and thus also D. fuscescens and montanum. 

 Concerning the liverworts, a citation from 

 Spruce is instructive : " I have a small tuft 



