CLAYTONIA GRONOV. A MORPHOLOGICAL AND ANATOMICAL STUDY. 



By Theo. Holm. 



(With plates 1 and 2.) 



I. CLAYTONIA AS A GENUS. 



A glance at the literature and a consideration of the species themselves must necessarily 

 convince even the most critical systematic that Claytonia, as heretofore defined, can not possi- 

 blv be confounded with Montia, nor Montia with Claytonia. They both have been excellently 

 described and seemingly well understood now for at least a century and a half. 



Sometimes the accumulation of new material with additional new species may alter the 

 views of the systematist in regard to the proper limitation of some genus, but this has not been 

 the ease with Claytonia. From the skillful treatment of such eminent systematists as Fenzl 

 and Gray, the genus has been received and explained as it always was, and has, of course, been 

 kept separate from the monotypic Montia. Though by no means a large genus, indeed rather a 

 small one, Claytonia represents an assemblage of species of marked variation in habit but with 

 the floral structure principally the same. As classified by Gray," the species are divided into 

 five sections based upon characters derived from the vegetative organs mainly: Euclaytonia, 

 the large-rooted C. megarrhiza, C Virginica, etc.; Limnia, the fibrous-rooted annual or peren- 

 nial C. Sibirica, C. perfoliata, etc.; Alsinastrum, the stoloniferous ('. Chamissonis; Naiocrene, 

 the bulbiferous C. parvifolia, and finally Montiastrum, the leafy-stemmed and alternate-leaved 

 annuals C. diffusa and C. linearis, of which the latter is, furthermore, distinct by the flowers 

 having the petals obviously unequal, but unguiculate as in the other species, and by the number 

 of stamens being sometimes reduced to only three. 



While thus the vegetative organs exhibit a very pronounced variation in Claytonia, the 

 floral structure appears essentially the same. The position of the calyx leaves is the same in all 

 the species enumerated by Gray, the anterior covering the posterior. The petals are always 

 prominently unguiculate and more or less coherent at the very base; their relative length may 

 be somewhat different within the same flower, as noticed in C. linearis. The stamens, normally 

 five, are inserted near the base of the petals, and finally the ovary is ovoid, bearing a long style 

 with three short branches, papillose only on their inner surface. It will be seen from this that 

 the flower of Claytonia throughout the genus — from Euclaytonia to Montiastrum, inclusive — 

 shows the same diagram, and that the modification sometimes observable in the relative size of 

 the petals and in the number of stamens does not disturb the primary arrangement of the indi- 

 vidual parts of the flower. 



It is now surprising to see that, notwithstanding such uniformity in floral structure, Claytonia 

 lias in late years 6 been divided and a number of its species been referred to Montia, with which 

 they have nothing in common. Here again the literature and a renewed examination of Montia 

 would have shown what Montia is and how correctly it was described and understood by Linnseus. 

 Let us then recapitulate some of the most essential points in the flower by which the monotypic 

 Montia differs from " all the other genera of the order Poi'tulacacese.'''' The exactly opposite 



"Proceed. Am. Acad., New Ser., Vol. 14, 1887, p. 278. 



b Synoptical Flora of North America, Vol. I, 1895-97, p. 272. 



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