- 7 6- 



parabolical bands, through regular graduation of branch sheaths. 



This is the typical plant, found from 38°-55° N. lat. and from 

 Ireland through Germany to the southern Urals, Persia, and 

 North Africa. Ascribed to the Great Lakes and Pacific Coast by 

 Milde, the former through error. All the American specimens 

 examined have proven to be varieties, and it is safe to assume 

 the type is not represented here. 



When we consider that the life of the spores is but a few 

 days, so that it is impossible to get them in a living condition 

 from the Pacific slope, the question of the peculiar distribution is 

 an interesting one. With ferns we might suppose the wind car- 

 ried the spores, but with Equiseta the chances against a ten-mile 

 trip, with male and female spores alighting near enough for fer- 

 tilization, are almost infinitesimal. As the American plant has 

 developed in special lines we should suppose long periods of time 

 to have elapsed since the separation, and we may well suppose it 

 to have been in glacial times, when so many plants were ex- 

 terminated over large areas. We thus have a measure of the 

 progress of species-making, and find that in this genus it is ex- 

 tremely slow. The presence of stomata on the leaves of the 

 fertile stems and their absence on the internodes would indicate 

 that the present habit of Equiseta, where the leaves are mere 

 appendages and the branches stomatose and chlorophyllose, is a 

 case of degeneration. I find no mention of these stomata by 

 any author save Buysson (Mon. Equis d'Eu.) I have seen none 

 on the European plants examined, but they are plentiful on the 

 American. The branches of the European plant often bear 

 secondary branchlets ; a condition which does not obtain in this 

 country, so far as available material, ranging from British 

 Columbia to San Diego, shows. 



Varieties. 



i. Brannii Milde. Sterile stems roughish, more deeply 

 grooved than in the type, light green, bearing a double row of 

 stomata on each side of the hollows. Branches 4-6 angled. A 

 cross-section of the stem shows a small fleck of green parenchyma 

 under each row of stomata. This has been found in Scotland, 

 but not elsewhere save in America, where it appears to displace 

 the type, being distributed along the Pacific coast line from Santa 

 Catalina Island (Trask), and San Bernardino, Cal., (Parish), to 

 British Columbia, where it is abundant about Victoria (Henry), 



