systematic account of the genus Struvea. 267 
Canary Island form under it as we have now done, after 
inspecting a specimen kindly sent us by Dr. Grunow. In 
1878 Zanardini described 1 a very beautiful minute form 
collected by Dr. Beccari, in New Guinea, under the name of 
N. tenuis. We have to thank Dr. Beccari for the opportunity 
of examining this species. 
Passing over for the present the hitherto unpublished form 
sent us by Dr. Grunow, under the MS. name of S', delicatula , 
KiAtz., var. Caracasanct, Grun., we now come to what is perhaps 
the most striking and beautiful of all forms of Struvea. Dr. 
J. E. Gray, in his paper on the genera Anadyomene and 
Microdictyon 2 , established the genus Phyllodictyon to include 
a very remarkable specimen collected by Mr. Menzies in the 
Gulf of Mexico in 1802, and preserved in the Herbarium of 
the British Museum. This very fragile specimen, large as it 
is (1 foot by 3 inches), is but a fragment of the whole 
plant, as the remains of the stalk clearly show. It was 
probably about an inch higher and six or seven inches in 
breadth. (See reduced Fig. 4 a.) Though so much larger than 
>S. macrophylla the texture of the frond is even more delicate. 
Dr. Agardh, in his recent monograph of Siphoneae, gives an 
account of the genus as known to him at p. 108. He merely 
enumerates the four species and one variety known to him 
(some of them by name only), and records his doubt as to 
whether they all belong to the same genus. So many more 
forms have become known to us, and we have obtained access 
to so much material, that we venture to hope that the follow- 
ing account may in some degree improve upon the unsatis- 
factory state in which Dr. Agardh was compelled to leave 
the genus. 
The Stalk consists of a single cell from its earliest stages 
up to the time of formation of the frond, when a transverse 
wall is formed a short distance below the base of the frond. 
The form of the stalk, however, differs greatly according to 
the species. 
1 Phyceae Papuanae Novae, in Nuovo Giorn. Bot. Ital. x. 
2 Journ. Bot. 1866, p. 69. 
T 2 
