F. Børgesen: Rhodophyceæ of the Danish W. Indies. 133 



unfortunately through a thallus in such a state, will only add 

 to the confusion. ^) 



The fruit of the Peyssonnelia are nemathecia with carpo- 

 spores and tetraspores raised above the surface of the frond. 

 By these nemathecia the Sqiiamariaceæ are easily known from 

 the Melobesiaceæ which they resemble so much in anatomical 

 structure. Scidiitz^) described the development of the procarp 

 and the auxiliary cells in Peijssofinelia but he gave no figures 

 and it is highly desirable that his investigations should be re- 

 peated. It is, however, very difficult to obtain good material. 

 The collection of Dr. Børgesen contains only nemathecia with 

 carpospores and tetraspores. 



But nemathecia with ripe carpo- or tetraspores are also a 

 character of importance when describing new species. While stu- 

 dying the Siboga material I had ample occassion to appreciate 

 their value, but the specimens collected by Dr. Børgesen are 

 more uniform in this respect than the East-Indian species. 



The collection of Dr. Børgesen is rich in Peijssonnelia. Maze 

 et Schramm in their "Les Algues de la Guadeloupe" mention only 

 Peijssonnelia Diihyi and Murray in his "Catalogue of marine 

 algæ of the West-Indian region" knows of no other representative 

 of this family. It is therefore not strange that Dr. Børgesen's 

 collection contains many novelties but, alas, also some plants 

 about which I feel uncertain. These algæ resemble well-known 

 species but are not exactly hke the type-specimens; if now the 



1) Continuing my research on the apical cell of the Peyssonnelia after 

 having finished this paper, I observed a stage of rest in the thallus 

 of P. rubra, followed by a period of intense growth. A section through 

 the margin in a state of rest, gave a figure resembUng the figure of 

 P. Boergesenii (Fig. 144). On this period of rest followed a period of 

 growth in which the topcell and the cells immediately following it, 

 wore difTereht aspects in succeeding longitudinal sections. I think that 

 these succeeding stages of growth and rest correspond with the con- 

 centric lines and smooth zones we observe in the thallus of P. rubra 

 that has, as we know, a turned up margin. The spot from where the 

 new growth begins, is attached by rhizoids to the substratum; the 

 young frond curves distinctly upwards but by succeeding growth it 

 stretches itself horizontally and will afterwards attach itself to the 

 substratum. I suppose that the concentric lines on the thallus coincide 

 with the spot from where the new growth begins, and which carries 

 many rhizoids. The intervening zones between two concentric lines 

 have as a rule far lesser rhizoids. 

 2) Schmitz, Untersuchungen über die Fruchtbildung der Squamarieen, 

 Sitzungsber. d. niederrh. Gesell. Bonn, 1879, p. 376. 



