M'^AB-^HemayJcs on the Leaves of certain Coni/erce. 211 



Pattoniana ; but in all specimens that have come under my notice 

 the hypodenn is developed, while Bertrand distinctly says, " Pas 

 d'hypoderm." Then the specimens of canadensis and Mertensiana 

 ezamined by me are quite distinct , In this case I think that Bertrand 

 has described Mertensiana for canadensis. Lastly, in his description 

 of Brunoniana and Sieboldii we are slightly at variance. 



The forms about which the greatest confusion has existed are 

 Hookeriana and Pattoniana. Both are, at first sight, very similar 

 in habit and in appearance, while their cones are also exceedingly close. 

 They are, however, readily separated by the structure of the leaf. In 

 Hookeriana the resin canal is separated from the fibro-vascular bun- 

 dles by a few parenchymatous cells, containing chlorophyll — a charac- 

 ter which does not occur iu any of the other species. The leaf is also 

 thicker, more tetragonous than Pattoniana ; the margins of the leaf are 

 entire, while in Pattoniana they are distinctly serrulate near the 

 apex. Both the species, however, agree in having stomata on the 

 upper as weU as on the under surface of the leaf. In Hookeriana the 

 hypoderm forms a nearly continuous row of cells beneath the whole 

 epidermis, giving such an appearance as might almost be produced if 

 the epidermis consisted of a double instead of a single layer of 

 cells. 



Taking all the characters, I would give the following table by 

 which to separate the different species : — 



I. Young shoots hairy. 



A. Resin canal separated from the sheath 

 of the fibro-vascular bundles by one or 

 two layers of large chlorophyU-bear- 

 ing cells ; leaf flatly tetragonous, the 

 hypoderma nearly continuous around 

 the whole leaf ; stomata on both sur- 

 faces. 



1. T. HOOKEEIAN-A. 



B. Eesin canal in contact with sheath of 

 fibro-vascular bundles. 



1 . Stomata on both sides of leaf ; 

 hypoderma well developed. 



2. Stomata on under surface of leaf 

 only. 



a. 'No hypoderma; margin of 

 leaf rough ; apex obtuse. 



h. H3rpoderma at margins of leaf, 

 and above midrib ; margia of 

 leaf ciliate ; apex obtuse. 



2. T. Pattoniana. 



3. T. CANADENSIS. 



4. T. Mekiensiana. 



