166 MEMOIRS OF THE NEW YORK BOTANICAL GARDEN [VOL. 10 





number of 



number of 



number of 



number <»f 





layers in 



layers in 



palisade 



sooner v 





adaxial 



abaxial 



parenchyma 



parenchyma 





hypodermis 



hypodermis 



layers 



layers 



S. campestris (fig. 9) 



2 



1-2 



3 



7 



S. connellii (fig. 11) 



3 







2 



19 



S. cucullatus (fig. 10) 



1-2 







2 



11 



S. huachamacari 



2 







9 



15 



S. kunhardiii 



2-3 



1-2 



3 



11 



S. obconicus (fig. 8) 



1-2 











14 



S. sericeus 



3 







2- 



12 



S. stipitatus 











-3 



11 



Variation among the species is found in other characters. Only one species, 

 8. cucullatus, has bundle sheath extensions, these being present on a few larger 

 veins. In S. obconicus and 8. huachamacari, a few mesophyll cells are converted 

 into thin-walled sclereids, mostly in layers near either epidermis. Bundle sheaths 

 in some species (8. kunhardtii, 8. campestris, 8. cucullatus, and 8. stipitatus) 

 have abundant fibers, particularly on larger veins. Where fibers are well devel- 

 oped in the bundle sheath, they often intervene between phloem and xylem of 

 the bundle itself. Some species are characterized by a sclerification of the lower 

 epidermis (8. cucullatus, and, to a lesser extent, 8. sericeus and 8. connellii). 

 Uniseriate hairs are retained on the lower surface of 8. sericeus leaves, although 

 the remaining species lose them early in ontogny, this variation being reminis- 

 cent of the situation in Hesperomannia (Carlquist 1957c). 



Each of the species of Stenopadus investigated, then, has a distinctive com- 

 bination of characters, so that identification of a species by means of leaf anatomy 

 would be quite feasible. The specializations in leaf anatomy have probably 

 occurred quite independently of other changes in this genus, and while the 

 different types of anatomy described are diagnostic, they do not fall readily 

 into a phylogenetic series or into sections of the genus. However, the conversion 

 of the lower epidermis into sclereids and the presence of diffuse sclereids in the 

 mesophyll would seem to be advanced characters. 



Reference to leaves of other Mutisieae, subtribe Gochnatinae, aids both in 

 showing that the patterns found in Stenopadus are relatively coherent, despite 

 their diversity, and in demonstrating that both less specialized and more ad- 

 vanced conditions exist in other genera. In Stifftia chrysantha (fig. 29), which 

 is considered related to Stenopadus, no true hypodermis is present, the meso- 

 phyll is only about 9 cell layers in width, with poor differentiation into palisade 

 and spongy tissue, and bundle sheaths are strongly fibrous. Bundle sheaths of 

 larger veins are often in contact with the adaxial epidermis. In another genus 

 of Gochnatinae, Anastraphia (fig. 28), a more specialized condition is seen. 

 Although the leaf is similar in thickness to that of Stifftia, a prominant hypo- 

 dermis is present. Moreover, the very conspicuous fibrous bundle sheaths form 

 extensions reaching from hypodermis to lower epidermis in all but the smaller 

 veins. Between veins, sunken pockets, covered with hairs and containing stomata 

 projecting above the epidermis, are formed. Such stomata have been reportd 

 by Solereder for the closely-related genus Gochnatia. A definite division into 

 palisade and spongy tissue occurs. In Anastraphia, then, some of the features 

 of Stenopadus and Stifftia leaves are present in an exaggerated form. 



