DFBLIN NATTRAL HISTORY SOCIETY. 37 



of tho tides that the Dublin coast has the reputation of being unprolific. We can 

 see, however, in the examples before us, what may be done by assiduity, by care- 

 fully examining what the waves will bring us, especially after storms. When I 

 was able to devote some time to the sea-shore, I found the second or third tide 

 (high water), after the storm ceased, to be the best time for examining the re- 

 jectamenta. Marine botany will be much benefited, if colluctors will care- 

 fully note every circumstance connected with the abundance of certain plants in 

 fiarticular spots, or seasons, and likewise the changes they may perceive in the 

 orms. The sportive character of the algse has led to much dispute — some bota- 

 nists insisting that certain species of other authors arc merely varieties. Doubtt 

 of this description will be more surely cleared up by the observations of many ob- 

 servers ; and it must also be borne in mind by botanists who are not very fami- 

 liar with alga), that many of them put on such variable appearances, according 

 to the season, as to lead to the belief that a summer specimen and a winter spe- 

 cimen of the same plant must be perfectly distinct species. Whilst speaking of 

 the abundance or scarcity of some plants at the usual season of their appearance, 

 I will read an extract from a letter I recently received from Dr. Cocks, which I 

 regard as most interesting, and I look upon it as a^ery remarkable fact in algo- 

 logy. He says — '• I have now had eleven years' experience in collecting, and 

 have gained a certain amount of practical information, which, I confess, I had 

 heretofore not sufficiently attended to. Observation and experience have taught 

 me that there is not the same regularity in the time ofappearanceof the marine 

 algte as there is in plants growing on terra firma, and that theterms annual, bien- 

 nial, and perennial, are not applicable to the former ; and that their erowth and 

 time of appearance are governed by laws, or influenced by causes which the al- 

 gologist, even of the present day, is unable to explain. It is quite true that, in 

 certain localities where I had been in the habit of gathering certain species for 

 two, three, and more years successively, when I have afterwards wanted to ob- 

 tain more, they had disappeared, and, in some instances, have never since been 

 found. In other instances, some plants, which were previously considered to be 

 extremely rare and scarce, only picked up at intervals far and few between, 

 have suddenly appeared in the greatest profusion. Dr. Budd told me that two 

 years ago, having found out where it grew, he could have dredged thousands of 

 specimens of Stenogramme interrupta. Last year I could myself have dredged 

 a like quantity of Sporochnus pedunculatus and Haliserit^ polypodioides, neither 

 of which species I ever took before to say plentifully. A few years ago the mud 

 bank at Cremil Passage was strewed over at low water with quantities of Sphse- 

 rococcus coronopifolius, since when I have only taken two specimens. You will, 

 of course, remember when we gathered such a quantity of Dasya arbuscula at 

 Firestone Bay. I have carefully hunted over the same ground every year since, 

 and have never seen a single plant ; even the very commonest plants sometimes 

 disappear for two, three, or more years — such as Delesseria hypoglossum, D. 

 ruscifolia, Nitophyllum punctatum, &c." Such is the experience of Dr. Cocks. 

 It would be very desirable for other algologists to note the appearance and dis- 

 appearance of plants from a locality, and then to endeavour to trace out the 

 cause. With the view of promoting the object of this paper — viz., the prepara- 

 tion of a list of all recorded algse found on the shores between Balbriggan and 

 Wicklow Head — I suggest that other collectors will look over their collections 

 and give our Secretary lists of their gatherings on those shores, that we may 

 have as large a catalogue as possible of the marine botany of the district. I 

 hope soon to increase the list, which, for the present, is confined entirely to Mrs. 

 Davy's collection ; and before concluding I would beg to draw the attention of 

 the members to the very beautiful and natural appearance of the specimens, 

 which were prepared after the method laid down in the '* Seaweed Collector's 

 Guide," by Dr. Cocks, of Devonport. 



