92 



NA TURE 



{June 4, 1874 



given. But e\-en more perplexing is the problem pre- | 

 sented by the survival of maritime plants upon some of 

 the highest and bleakest mountain-tops. In such por- 

 tions the Coclilearia or scurvy grass, the Ariueria or 

 sea pink, with Silciie inarilima and Plantcigo niaritiina, 

 are found abundantly. They are poor dwarfed forms, it 

 is true, when compared with their contemporaries 

 on the coast, so that the latter habitat is evidently 

 more congenial to them than the bleak uplands. De- 

 scendants of the old arctic flora once indigenous in 

 this countiy down to the sea-level, as it is in northern 

 Scandinavia at the present day, how have they come to 

 be left on our mountain tops ? Were they maritime 

 plants originally, and have they been carried up by the 

 gradual elevation of the land 'i This would involve a 

 former submergence of the country to a depth of at least 

 4,000 ft. — a limit much beyond that suggested by other 

 geological evidence. Or did they form part of the gene- 

 rally distributed flora whereof some species keeping to 

 the shores have been able amid bare rocks and salt spray 

 to maintain themselves there ever since, while farther 

 inland they have succumbed to the march of the invading 

 Germanic flora, and have been allowed to struggle on in 

 dwarfed and stunted forms only on the bare chill moun- 

 tain tops, whither the invaders did not care to pursue 

 them 'i 



Some light might possibly be cast on these questions 

 by an examination of the contents of our older peat- 

 mosses. There is reason to suppose that some of these 

 mosses may date back into Glacial times. It would be 

 interesting to discover whether among the plants whose 

 remains went to form the peat any northern species 

 could be detected no longer living in this country, even 

 in our Alpine zone. This line of inquiry is now being 

 prosecuted in Scandinavia, and it is suggested to the 

 botanists of Scotland as a fit subject for their attention. 



The more purely geological work by the brethren of 

 the hammer during this excursion, whether when with the 

 botanists among the Grampians or afterwards by them- 

 selves along the shore between Dunnottar and Aberdeen, 

 is hardly appropriate in a communication to the Botani- 

 cal Society. 



ON THE FERTILISATION OF CERTAIN 

 LABIAT.E 



T N the early part of April of the present year I had an 

 ^ opportunity of watching somewhat closely the mode 

 of fertilisation of some species of Labiata;, on which'some 

 notes may be interesting. The species observed were the 

 three most abundant of the early flowering representatives 

 of the order, Lainiicm album, L. purpureiim, and Nepela 

 gleclwma ; the cost of observation a bank covered by the 

 three species growing completely intermixed, just outside 

 a cottage-garden where were several hives of bees ; the 

 time occupied, several hours on three sunny mornings. 

 The point which interested me most was the constancy 

 with which the same species of insect confined its visits 

 to the same species of flower, notwithstanding the close 

 proxmiity in which the three were growing, this being 

 perfectly m harmony with Mr. Traherne Moggridge's ob- 

 servations of a similar character respecting the visits of 

 insects to I'umitories and other flowers. 



My conclusion is not based merely on actually noticing 

 the visits ol insects, but on the microscopic examination 

 of the pollen collected on the captured insects. For this 

 purpose the pollen- grains of the three specits named offer 

 unusual facilities, those of Lamimn album being yellow, 

 of L. purpurcum red, and of Nepela glechoina white. 



In Lainium album the length of the style is such as to 

 bring the btigmatic surface exactly on a level with the 

 anthers 01 the shorter pair of stamens, as represented in 

 Fig. I ; one branch of the style is nearly straight and is 



hidden among the anthers, the other projects at right 

 angles into the opening to the tube of the corolla, so that 

 it must necessarily be struck by any insect entering the 

 flower. The only visitors to the flower seen were tv- 

 species of humble-bee, Bombus pratorum* (female) ami 

 Antlwphora retusa (female), the former in large number, 

 the latter much more rarely. From the position of tli 

 stigmatic surface, both it and the stamens must be stru^ 

 by about the centre of the head of the bee ; and it was 0.1 

 this part that the greater number of pollen-grains were 

 found, and proved to belong exclusively to this species. 

 In no single instance was a hive-bee seen to visit the 

 flowers; Miiller states that they obtain the honey from 

 this species entirely by sucking it through holes bitten in 

 the corolla by Bombus terrestris. 



In Lamium purpureuin the difference in length be 

 tween the two pairs of stamens is less considerable an^l 

 the anthers are consequently closer together, both branches 

 of the style being bent forwards into the mouth of the' 

 corolla, as shown in Fig. 2. Although hive-bees were 

 constantly hovering over the flowers, in no single instance 

 did I see either them or the humble-bees visit this species ; 

 the only insect observed to settle on it being a butterfly 

 ( Vanessa urlica) twice. 



The position of the parts in Nepela glechoma is very 

 different. The two pairs of anthers are at a consider- 

 able distance from one another (Fig. 3), and the length of 



Fic. 2. 

 stamens, style, £ 



id sti^mi. Fig. 2. — Lamiiu 

 , Fig. 3. — Nepela glecltama 



Fig. i.—Lamuim 



purpitrcifm ; stamens, style, and stigni 

 stamens, style, and stigma. 



the style is such as to bring the stigmatic surface con- 

 siderably beyond the longest pair, and projecting beyond 

 the mouth of the much smaller corolla. The flowers 

 were profusely visited by the hive-bees from the other 

 side of the hedge. On no single occasion did I see the 

 'Bombus pi-ali.<rum, of which such numbers were flying 

 about, even attempt to enter the flower, and the smaller 

 species, Antliophora retusa, only twice ; and on each of 

 these occasions she immediately came out again and 

 began industriously to wipe the pollen off her head with 

 her fore-legs, as if she disliked it. Owing to the much 

 smaller size of the flower, and the greater length of the 

 style, the part of the body of the bee touched by the 

 stigma is very different to that in the Lamium album, 

 namely, the back of the neck or even of the thorax. 

 Hence even if the insect should visit the two species on the 

 same journey — which, I should infer, is not usual — the 

 pollen of one species would not easily be wiped off on to 

 the stigma of the other. I did not observe any plants of 

 the ground-ivy with the "female" flowers described_by 



* In this and all other instances I am indebted for the deterniina'* 

 the insects to the kindness of my friend Mr. Edv\-ard Newman. 



