INFLOEESCENCE-COKOLLA. 



of, th 



specimens of an exceptional, but yet distinct, centrifugal opening (P. ***** 



a centrifugal inflorescence is constantly present in and i. u7l . • 



Arctic group Hirmtw. J P ' and 1S h ' ghI y cha «ctenst.c 



The calyx consists of a tube which may be ovate (P. EhmOl campanula (P 



grmna), yhndnc P PerrotleUi), or subinflated (P. Wallicku), and of t eth w ich n ay be 

 minute (P. ^W/ote), but are generally distinct, and then are either oblong o 

 triangular with a broad base, or ovate with a n*™,™ k™ m,._ ,. . . *\ u 



ovate with a narrow base. The tub 



in consist 



ence from thinly meinbranous (P. rex), r membranous (P. fragUis), to herbaceous 

 P. f«*V« thickly herbaceous (P. Wfc), and may sometimes even be sub-coriaceous 

 (P. mtegnfoia). In a few cases tube and teeth are of the same consistence As <i 

 rule in calyces with wide-based teeth the margin, and in those with na 

 teeth the whole tooth, is of firmer consistence than the tube 



row- based 



The tube is always longitudinally nerved; five strong main nerves pass upwards 



into 



the calyx teeth with usually five slender intermediate nerves that fork near the limbus 

 into marginal nervules for two adjacent teeth. As a rare occurrence these secondarv 

 nerves may all be absent, but as a rule where the upper tooth is weak the upper main 

 nerve is of the same thickness as the adjacent secondary nerves, while when tho upper 

 tooth altogether disappears and the calyx is 2-dentate, these adjacent secondary nerves 

 are not traceable, and the posterior nerve may either pass entirely into one lateral tooth 

 (P. rex), or more usually may fork into the two lateral teeth (P. carnosa). The longitudinal 

 nerves may be unbranched (P. rex), but usually those that pass directly into the teeth 

 give off lateral nervules that may be confined to the teeth only (P. verticillata) or 

 extend throughout the upper third or half of the tube (the most usual condition), some- 

 times even to the base of the tube (P. dolhhorrhisa). The normal number of teeth is 



five, but the upper tooth, except in a small number of species with triangular teeth is 



distinctly smaller and less incised than the other four. Of the remainder the two nearer 



the upper tooth are almost always distinctly larger than the anterior pair. But often 



there are only three teeth (P. siphonantha, longiflora), in which case the two lateral pairs 



are confluent, and sometimes only two (P. carnosa, Collettii, curvipes) from the further 



abortion of the naturally weaker upper tooth, or very rarely (as in the already quoted 



case of P. rex) from the absorption of the upper tooth in one or other of the lateral 



ones. The lateral nervules of triangular or oblong teeth anastomose with the marginal 



branches derived from the forking secondary nerves ; the lateral nervules of narrow-based 



ovate teeth are disposed like the nerves of a small leaf or bract. The length of the 



teeth relatively to the calyx tube may vary considerably in the same species (P. bicornuta), 



but the proportions of the teeth to each other remain very constant. But it has to be 



noted that in normally 5-toothed species the lateral pairs of teeth on one side or on 



both may be conjoined (P. Elwesii, megalantha), while similarly the lateral teeth of 



normally 3- or 2-toothed species (P. carnosa, longiflora) may on one side or on both be 



divided. Besides beinef toothed, the limbus is usually cleft in front, occasionally to the 



base (P. rex), sometimes | to f of its depth (P. Elwesii, furfuracea), but usually only from 

 to \, and occasionally the limbus is not perceptibly cleft (P. gracilis, gruina). In 

 2-dentate species it is cleft also, though less extensively, behind. The margins of lanceolate 

 or oblong teeth may be entire, or serrate at the apex only (P. Oederi), or throughout 

 P. Clarkei); those of ovate teeth are always dentate or incised, the segments not 

 infrequently being mucronate. These dentations may be erect, or deflexed at the 

 tip only, or altogether, and sometimes the whole tooth is deflexed. These conditions give 



