i84 AN GIOSPERMAE— DICOTYLEDON ES 



66i. Pentstemon Mitch. 



Literature. — Delpino, ' Ult. oss.,' I : Errera, Bull. Soc. roy. bot., Gand, xvii, 

 1879 ; Loew, ' Bliitenbiol. Beitrage,' I, pp. 31-40, Bot. Centralbl., Cassel, Beih. xvii, 

 1904, 'D. Bestaubungseinricht. v. Pentastemon Menziesii u. verwandt. Arten,' in 

 Festschr. fiir Prof. Ascherson, Berlin, 1904; Pasquale, Atti congr. botan. internat., 

 Geneva, (1892) 1893, pp. 553-60; Familiar, Inaug.-Dissert., Munchen, 1896; 

 Heinricher, Sitz-Ber. Ak. Wiss., Wien, Ixxxvii, 1883; I. Robinson, Ost. bot. Zs., 

 Wien, xlvi, 1896, p. 398. 



Protandrous flowers with concealed nectar ; stamens and style displaced. The 

 posterior stamen is transformed into a long staminode, sharply bent at its base, and 

 traversing the corolla-tube obliquely until its tip lies on the central lobe of the 

 lower lip. 



Comparative studies of as many species as obtainable have recently been 

 made by Loew, with regard to the nectaries and staminode of this genus, which 

 has been the subject of so much oecological work. The material was partly 

 obtained from plants cultivated in the Berlin Botanic Garden, and partly from the 

 herbarium of the Royal Botanic Museum in Berlin. In most species the nectaries 

 are on the outer side of the bases of the two upper filaments, and usually consist 

 of a large number of closely crowded unicellular epidermal papillae, of glandular 

 nature. In some species (e. g. P. Cusickii A. Gray, P. diffusus Dougl., P. 

 gracilentus A. Gray and P. Rattani A. Gray) these papillae are divided by 

 longitudinal septa into two or four daughter-cells, and resemble the stalked 

 glandular trichomes found on the calyx, inflorescence axis, and the vegetative 

 organs of many Pentstemons. The latter, however, possess a much longer stalk- 

 cell, though transitions have been observed between the two kinds of trichome. 

 Herbarium specimens of a number of shrubby Californian species belonging to 

 the section Fruticosi were examined (P. cordifolius Benth., P. ternatus Torr., 

 P. breviflorus LindL, antirrhinoides Benth., P. Rothrockii A. Gray and P. Lemmoni 

 A. Gray), and in these the nectar-secreting arrangements differ from that just 

 described. Here there are no glandular papillae on the bases of the two upper 

 filaments. The bases of all four stamens and of the staminodes are greatly 

 broadened, and their margins more or less closely beset with stiff protective hairs. 

 These parts clearly serve as covers for nectar secreted elsewhere, and the nectary 

 is either represented by the well-marked annular hypogynous disk sometimes 

 present or by the base of the corolla. The herbarium material employed did 

 not allow of more accurate determination. 



There are great variations within the genus Pentstemon as regards the 

 staminode, as well as with reference to the nectaries, and these are obviously 

 related to the method of pollination. It is sometimes a short useless appendage, 

 sometimes a long glabrous thread. It may be beset with double series of hairs, 

 sometimes in an almost comb-like fashion, or it may possess a unilateral series 

 of short stiff bristles. Its tip may be spatulate or spirally coiled. The height 

 of its insertion is equally variable, for this may be close to those of the fertile 

 stamens or at some distance away. Errera regards the characteristic bend found 

 in many species as an arrangement for obliging visitors to suck the nectar at 



