36 THE JOURNAL OF BOTANY 



such phytosynthetic bubbles is that of Colpomenia sinuosa, a Medi- 

 terranean Phseosporean, which appeared in 1906 at Vannes in the 

 Gulf of Morbihan (Belle Isle), growing attached to oysters. The 

 plant became an economic nuisance, and is known as the Oyster-thief 

 (Voleuse dliuitres) (cf. Cotton in Kew Bulletin, 1908, p. 75). The 

 thallus of pareitchymatous organization and papery texture is hollow, 

 and may attain the size of a hen's e^g or tennis-ball, as a " balloon." 

 On active photosynthesis in shallow water the cavity so fills with 

 internal gas-bubbles that on the return of the tide the inflated 

 balloons weigh the young oysters to which they are attached and 

 float them out to sea. The number of oysters so carried off was so 

 considerable that attempts were made to recapture them by nets, 

 while faggots were dragged over the beds in the hope of tearing the 

 thallus-balloons. The story is usually approached from the stand- 

 point of the oyster-owner, but it shows that Colpomenia merely 

 attaches to the oysters in such a station for want of better anchorage, 

 while the final disaster is possibly greater in the case of the plant 

 than in that of the animal. The point of interest is that the majority 

 of the oysters so weighed are lost, not cast on shore, and the effect of 

 weighing moorings generally is to be carried out to deep water rather 

 than to be thrown up. There seems to be no means of obtaining an 

 estimate as to the relation between the amount of sea-weed detached 

 and throw^n on shore and that drifted back to deep water, to exist as 

 *' loose-lying " vegetation, or to sink and die in the open sea. 

 Immense quantities of weed thrown on the beach by one storm may 

 be swept out to sea again by a succeeding tide. The amount of 

 weed thus cast up as flotsam and jetsam which might be economically 

 utilized is probably but a very small proportion of the wastage of the 

 sea, as expressing the amount of increase over what the station will 

 carry. 



Further observations on the lifting of stones of considerable 

 size have been recently made by Mr. Spence at Orkney in the case of 

 the larger Laminarians {cf. Journ. Bot. 1918, p. 281). Thus 

 L. Cloustoni, thougli usually growing on rocky bottom will bring 

 ashore stones of 6-8 lbs. weight. In one case 9 large Laminarias, of 

 which one was L. fiexicaidis, were brought in attached to a stone of 

 over o6 lbs., or an average of 8 lbs. per plant, whose weight might be 

 3-5 lbs. each. i<iaccorlii za bullosa more frequently brings adherent 

 boulders as rounded blocks of 50-60 or even 80 lbs. ; a good example 

 of 9 Saccorhizas brought a rounded block 12 in. by 11, weighing over 

 56 lbs. From such data it would appear that one of these larger 

 Laminarians with full head of fronds presents a form-resistance 

 enabling it to sustain in a rough sea a stone equal to twice its full 

 Aveight (averaging 8 lbs.) ; or a plant of specific gi-avity little more 

 than that of the salt water, may carry a stone equal in the water to 

 the true weight of the former. Saccorhiza, in fact, is to be regarded 

 as an alga specially adapted by its remarkable hapteron-bulb. which 

 replaces the usual crampon-system, to grow among loose boulders, as 

 a plant of mare marked individuality'^ than the gregarious L. Clou- 

 stoni. 



These observations again do not refer to the rolling of still larger 



