472 Observations on some British Plants. 



granular, colourless matter. But as the cell advances in growth, 

 this granular substance separates from the division-walls and the 

 cell lengthens on both ends from it as a centre ; it is attached 

 only to the wall, and sends out along the wall threads of slime, 

 which by iodine become very visible, although the eye alone is 

 sufficient for observing them. Fig. 18 represents a young branch 

 with the nuclei attached to the walls of the cells and their threads 

 of slime. Finally, in the mature hair, nuclei and slime-threads 

 disappear, and the hair looks like that represented by fig. 21. 

 VI repeat, that the hairs of Leathesia tuberiformis, Vhorda 

 Idmentaria, Cladostephus spongiosus, Cystoseira granulata and 

 Polysiphonia urceolata, have nuclei attached to the wall, and that, 

 with the exception of Chorda lomentaria, where 1 did not observe 

 it, threads of slime, partly anastomosing, spread from the nucleus 

 along the walls of the cells. These results agree entirely with 

 Nageli^s observations (/. c. p. 226) on the hairs of Laurencia 

 dasyphyllttj Ryfipklcea tinct., Rhodomela pinastroides, and a 

 species (?) of Hutchinsia. But when Nageli adds of the nucleus, 

 " It displays itself as a transparent utricle with a delicate mem- 

 brane and a small point-like nucleolus," I must avow, that I 

 have never observed this. The nuclei which I saw were all 

 more or less solid heaps of granular slime, in all stages of 

 growth. 



It is singular that it seems to be a particular property of the 

 hail's and hair-like bodies to have the nucleus attached to the 

 wall, so that if a plant has in the stem free, central nuclei, but 

 the points of its branches are drawn out in a hair-like way, these 

 points acquire nuclei, attached to the wall. Ectocarpus silicu- 

 losus is an instance of this sort. It has in the stem free central 

 nuclcatj but in the hair-like points of the branches, beyond the 

 cells, containing the sporules, it has nuclei attached to the wall. 



fmaoi 'j XLI. — Observations on some British Plants, qfiiljtHJ 

 ^3woJ By George A. Walker-Arnott, LL.D. &c. I ^m^j 



89mq8 ^ ike Editors of the Annals of Natural Histoid y'}\^^'^ 

 iifiTi&^NTLEMEN, baiO'iM) 8i]W do Glasgow, Nov. 11, 1850.;.^ 

 In a notice of the new ecfifion of the * British Flora' in your 

 last Number, p. 380, a note is added, that '* it is sufficiently 

 known that I alone am really responsible for nearly all the 

 additions and alterations :" this it is not my present purpose 

 either to affirm or deny, but I willingly hold myself responsible 

 for all the errors or " blemishes " the writer has pointed out, 

 particularly as I am, as yet, so little convinced by his arguments, 

 that I would, if a new edition were called for tomorrow, be dis- 



