110 



R. A. GRAHAM 



(3) It is clear, from his descriptions of other mints, that Linnaeus accurately recog- 

 nised capitate and verticillate types of inflorescence. Had this specimen been the original 

 M. aquatica it is hard to understand why he used the words florihus capitatis when florihus 

 verticillatis would be much more correct. 



(4) Linnaeus accurately described his M. hirsuta as florihus capitatis. His specimen 

 of this is a normal but very hairy water mint. It is described as differing from M. aquatica 

 only in being more hairy and with shorter petioles, and yet his specimen of M. hirsuta is 

 very unlike that named as M. aquatica. 



(5) Water mints apparently always have a hairy calyx tube. For this reason I do 

 not think that " Planta non hirta " can imply a wholly glabrous state. But the specimen 

 named M. aquatica is altogether too hairy reasonably to be described in these terms. 



From Linnaeus' description of M. aquatica and from his comments in comparison 

 with M. hirsuta (see under var. hirsuta below), together with inferences from his specimen 

 of the latter mint (No. 730/8), the original M. aquatica L. can be suggested as a water 

 mint with the following characters : Whole plant suhglahrous in appearance, though not 

 wholly so in detail; leaves ovate, serrate, hasally rounded to ±: cordate, on petioles long 

 enough to be obvious; inflorescence either a terminal capitulum only, or with underlying 

 verticils which may be contiguous to give the appearance of a blunt spike. His specimen 

 probably owes its identification to some character in which it appeared to Linnaeus to 

 agree with his original M. aquatica. 



Many British water mints, especially from riparian areas, are largely subglabrous 

 and can, in my opinion, be regarded as typical of Linnaeus' original M. aquatica. I have 

 placed in the Oxford herbarium an example which indicates my conception of a typical 

 plant in every character except that the upper part of the stem is perhaps a little too 

 hairy although the whole plant is outwardly subglabrous. Gathered from Marlow river- 

 side, Bucks., v.c. 24, it can be described as follows : 



Stem green, branched, a little bearded at the nodes, otherwise almost glabrous below 

 but becoming progressively more hirsute upwards with retrorse, white hairs; internodes 

 up to 5-5 cm. Leaves ovate to oblong-ovate, thin in texture, obtuse to sub-acute, abruptly 

 rounded and sometimes it truncate at the base, usually with a small wedge at the junction 

 with the petiole; up to 5-5 X 3-3 cm. ; generally subglabrous but with whitish hairs on 

 the nerves of both surfaces - more numerous on the upper, more immature leaves ; ser- 

 ratures shallow, blunt, forward-directed, + regular in spacing, up to 1 mm. deep, and 

 to 14 in number. Petioles up to 2-5 cm. long, with a few, scattered, white hairs. In- 

 florescence consisting of a terminal, Jz rounded capitulum of medium size, 2 cm. in 

 diameter, with one pair of under-lying, non-contiguous, axillary, shortly-pedunculate 

 verticils. Calyx tubular, shortly ciliate with i ascending hairs. Pedicels rather shaggy 

 with retrorse, white hairs. Corolla with a few scattered hairs externally. Stamens exserted. 



Whereas typical M. aquatica L. is suggested as a mint with the general characters set 

 out in the previous paragraph, it will become clear to anyone who consults the many 

 specimens in our national herbaria and in private collections that water mint is extremely 

 variable. The following paragraph is therefore devoted to a description of water mint 

 forms in the aggregate, indicating variation in certain characters. 



Stem squarish, simple or branched, green to red, glabrous to densely hairy with 

 long, white hairs. Leaves orbicular to narrowly elliptical, very acute to rounded at the 

 apex, cordate to long attenuate at the base, glabrous to densely pilose - the lower surface 

 having sometimes a matted indumentum giving the appearance of a coarse tomentum (the 

 upper, less mature leaves tend to be more hairy than the lower which have arrived at 

 full maturity); serratures very few to very many, shallow to deep, sometimes salient, 

 blunt and sometimes ib crenate to jagged. Inflorescence essentially capitate, of either a 



