1891.] A key to the North American Labiate. 49 



of sporodochium more highly magnified, showing mass of loose spores and scurfy 

 matter on top, sparingly mixed with the characteristic hairs; 4, a group of 

 basidia with the hairs highly magnified; 6, a branching basidum and loose 

 spores very highly magnified. 7, Macrosporlum puccinioides Ell. and Anders., on 

 dead stems of Bigelovia (?) Montana, Kelsey, slightly magnified; 8, a group of 

 forming and young spores rising from the interwoven threads forming the sub- 

 stratum of the sporodochium; 9, a cluster of mature spores; 10, two mature spores 

 showing the stipitate base; 11, three young spores, showing the remarkable re- 

 semblance to Puccinia spores. 12, Pestalozziella Andersoni Ell. and Evrht. , natural 

 size on small leaf of Apocynum cannabinum; 13, vertical section through a leaf 

 showing the destructiveness of the fungus; highly magnified; 14, five spores 

 more highly magnified. 



A key to the North American genera of the Labiate. 



ALFRED C. STOKES. 



While the keys to this group in Gray's Manual and in other 

 botanies are praiseworthy in many respects, they are not 

 adapted to use in the field, unless that use is to be limited to 

 those who have become experts. To the beginner and the 

 amateur they are disheartening. The following compilation 

 from the Synoptical Flora is in reality Professor Gray's alone; 

 all that I have done is to attempt to use only the more obvious 

 characters that will lead to the genera in the most direct way. 

 That even so limited a paper as this is free from errors is not 

 expected. Notice of blunders will be gladly received from 

 those that may try to use the key. 



I. Ovary merely 4-lobed, not deeply 4-parted (A). 



II. Ovary deeply 4-parted (B). 



III. Ovary deeply 5-lobed; corolla almost regular, 5-parted, blue 



.... Isanthus, 3. 



' A Stamens exserted from the cleft in the upper lip of the cor- 

 olla (1)). 



A Stamens not exserted from the cleft in the upper lip of the ob- 

 scurely bilabiate corolla (a). 



a Calyx deeply 5-cleft, regular, lobes lanceolate, twice as long as 

 the turbinate tube; corolla nearly salverform Tetraelea, 1. 



a Calyx barely 5-cleft; corolla tube narrow; filaments long ex- 

 serted Trichostema, 2. 



b Corolla upper lip deeply cleft, the lower declined, lateral lobes 



united to it. . . .Teucrium, 4. 



b Corolla upper lip short, truncate; lower lip large, middle lobe 

 emargmate or 2-cleft.. . .Ajuga, 5. 



