Dr. R. Caspaiy on the Hairs of marine Alga. 465 



XL. — On the Hairs of marine Alga and their development. 

 By Dr. Robert Caspary. 



[With three Plates.] 



The following observations, which by no means exhaust their 

 subject, are destined to direct the attention of botanists to one 

 point of marine algology, which up to this time has scarcely 

 been noticed, viz. the characters of the hairs of the Seaweeds. 

 A person, who from other parts of botany knows how much 

 attention is paid to the external covering of plants, as well by 

 the physiologist as by the merely descriptive botanist, and enters 

 upon marine algology with the expectation that the external 

 covering here will be the more scrupulously noticed, as everj'^- 

 thing is treated with the microscope, will find himself totally 

 disappointed. I need scarcely observe, that in other parts of 

 botany even the recognition of the species often depends upon 

 the hairs ; I mention only the genera Mijosotis, Leontodon, Oro- 

 banche, Polypodium, &c., and that none of the better books ever 

 fail to notice them. Many of the marine Algse have a very 

 peculiar external covering, which will, I trust, before long not 

 only be found of importance to the physiologist, as it partly 

 already has been, but also to the descriptive botanist in 

 establishing striking characters for the recognition of genera 

 and species. By some of my friends to whom I have mentioned 

 the importance of the hairs in marine Algse, the objection has 

 been raised, that they are not essential. But what is essential ? 

 Without entering upon metaphysical speculations, I trust that 

 the reader will agree with me, that everything in a plant is 

 essentia], which under regular and ordinary circumstances is 

 always produced by it. But if this is the explanation of the 

 notion of essential as far as a botanist wants it, then the hairs 

 of the marine Algse are no longer to be overlooked or to be 

 treated as inessential, as every plant which is not taken from 

 high-water mark or a very exposed situation, but from a sheltered 

 pool or deeper water, will invariably, if hairs at all are produced 

 by it, exhibit them. I beg to observe, that the following ob- 

 servations were all made on living plants and with sea-water. 

 Those who would criticise them must not judge from dry spe- 

 cimens, to which in describing Algse recourse should be had 

 only in utter want of fresh ones, from reasons so obvious that I 

 need not to state them. Descriptions and representations not 

 taken from the living plant are in algology of no value whatever 

 to the physiologist, and of very little indeed to the systematic 

 botanist. 



Ann. ^ Mag. N. Hist. Ser. 2. Vol. vi. 31 



