Nitrogen-Metabolism on Land and in the Sea. 125 
Examination of the seedlings of Pilularia shows that the 
development of the vascular system takes place along lines 
essentially similar to those described for Polypodiaceae. It is 
hoped that the investigation may soon be extended to Marsilea, 
a plant of obvious interest in connection with “ stelar ” questions. 
In the present brief note a discussion of the results arrived at 
is quite impossible. It will be sufficient to add that the early 
appearance of internal phloem in the primary vascular rod 
(protostele), and the simple processes involved in the subsequent 
elaboration of the vascular system of such a plant as Doodia aspera ( 
most strongly support the contention of Farmer and Hill that in 
dealing with all so-called “ stelar ” questions, we have to confine our 
attention to the consideration of tissues of two, and only two 
categories, viz., vascular and non-vascular. 
Royal College of Science, S. E. Chandler. 
May, 1904. 
NITROGEN-METABOLISM ON LAND AND IN THE SEA. 
T is evident that the general metabolic cycle in the ocean must 
be the same as that on land. In both, constituents of the air 
and of water, together with various inorganic substances are built 
up by plants into living material. The animals live directly or 
indirectly on the vegetable substances so produced and at their 
death are resolved again into their inorganic constituents, with 
which the cycle of metabolism begins afresh. 
The plant-life of the ocean falls easily into two main divisions : 
one, which includes the larger forms, the fixed algae, fringing the 
coasts; the other, the smaller, microscopic, free-floating forms 
(chiefly Peridineae, Diatoms and small Flagellata), forming the 
vegetable plankton. As in the case of trees on land, the fixed algae, 
though by far the more striking, are of much less importance from 
the point of view of the animal food supply of the ocean. It is on 
the vegetable plankton, as on the less conspicuous herbage on land, 
that the animal life is mainly dependent. 
Owing to the smallness of many of the vegetable plankton 
organisms the balance between animals and plants, which is an 
obvious physiological necessity, is sometimes apparently absent. 
Thus Brandt has found in the bay of Kiel in many cases that more 
than 60 or 70% of the dried “catch” consisted of animal substance. 
It is obvious that the “consumers” could not, for the long periods 
