270 


Comparative Embryology of Plants. 
if T is generally acknowledged that land-living plants 
have sprung from some algal source: that 
the land was invaded and that the invaders show 
form and structure adapted to sub-aerial life. If 
this be true, land-plants should still show features 
indicating their origin, and such characters should 
be expected to appear in their embryology. The 
higher algal structure is generally referable to the 
filament or row of cells with a free apex, and a base 
attached to the substratum. The individual com- 
monly springs from such a source, amplified in various 
ways to form the adult. It is found that the com- 
parative embryology of land-plants up to the seed 
plants themselves also suggest a filamentous origin. 
The apex is defined by the very first segmentation of 
the zygote: the base in bryophytes is the base of 
the sporogonium : in leafy plants it is the suspensor, 
recognised by Lang as a vestigial organ. He held 
that its presence is a last indication of the filamentous 
structure, a juvenile stage rapidly passed over in 
them, and often suppressed. The body thus visual- 
ised between apex and base may be called the primi- 
tive spindle. 
Two distinct types of its orientation exist. In the 
first, the apex is directed to the neck of the arche- 
gonium (exoscopic). That is the characteristic of 
all bryophytes, and of Equisetum, Isoetes, and 
Tmesipteris. In the other, the apex is directed 
away from the neck (endoscopic), and it is found in 
lycopods, some primitive ferns, and in all seed-plants. 
An intermediate pcsition is seen in certain ferns, 
including all the later types. In fact, with some 
exceptions, the distinction follows the major lines 
of affinity in the vegetable kingdom : therefore it is 
probably of high morphological importance. The 
interest will centre round the exceptions: and their 
explanation is probably to be found in the varying 
orientation of the archegonium. 
The end of all higher embryology is the establish- 
ment of a leafy plant with its shoot pointed upwards. 
1 Abstract of the presidential address to the Royal Society of Edinburgh, 
delivered by Prof. F. O. Bower, F.R.S., on October 23, entitled ‘‘ The Primi- 
tive Spindle as a Fundamental Feature in the Embryology of Plants” (Proc. 
Roy. Soc. Edin., vol. xliii. part 1. p. 1); 
NATURE 

[FEBRUARY 24, 1923 

Where the archegonium points downwards, endo- 
scopic orientation will lead directly to this result, 
but if the archegonium be inclined or inverted, the 
spindle will have to be inconveniently curved to 
secure that end. Many lycopods, selaginellas, and 
some ferns show awkward curvatures of the embryo 
to carry it out. 
in these the awkward curves are absent. 
gested that the inconvenience has been removed by 
abortion of the vestigial suspensor, which tied their | 
ancestors down to the endoscopic orientation so — 
inconvenient where the archegonium points obliquely, 
or actually upwards. The horsetails, Isoetes, and 
the leptosporangiate ferns would all be derivative in 
this respect. Having no suspensors, their initial 
polarity could be freely determined so that the 
apex would point from the first in the convenient 
direction. 
Upon the spindle thus defined, whether complete 
or abbreviated by abortion, straight or curved, the 
appendages are attached. The leaves are possibly 
in phyletic origin, the results of distal dichotomy of 
the apex. 
and together with the axis they constitute the terminal 
bud. The first root is always of lateral origin in 
pteridophytes, and phyletically it is an accessory 
organ, absent in fact in the most primitive types. 
It is only in seed-plants that it appears to continue 
the axis downwards. Lastly, the “ foot,’’ which is 
so inconstant in its development, is clearly accessory 
also, in fact a sucker formed laterally where it is 
required. So the primitive spindle, defined by the 
apex of the shoot and with the tip of the suspensor 
as its base, appears to be a real and constant feature 
in the embryos of plants. But as it is liable to be 
abbreviated by the abortion of its base, and com- 
plicated at the apex and also lower down by the 
formation of lateral appendages of various sorts, it 
is often effectively disguised. Nevertheless, an 
adequate morphological and biological comparison 
of plants suggests that all their embryos are referable 
in origin to a filamentous source, such as is prefigured 
in the alge. ; 
Exploitation of South African Fisheries.’ 
By Prof. J. STANLEY GARDINER, F.R.S. 
TRE Union of South Africa has consistently 
endeavoured to pursue a far-sighted policy 
in reference to the exploitation of its seas. A survey 
with the S.S. Pieter Faure was made twenty years 
ago and resulted in the starting of a trawler industry, 
while a series of volumes were published dealing 
with the fauna of the grounds. In 1920 the Union 
hired a whaler, the Pick/e, 102 feet long; 20 feet beam, 
and 11} feet draught, equipped the vessel with trawls, 
warps, and sounding gear, and sent it to explore 
the fishing area, Dr. Gilchrist being the scientific 
adviser. The ship was commissioned for 20 months. 
It was singularly unsuited in many respects for 
trawling in commercial fashion, being of too shallow 
draught and not of the right build, only hauling 
an otter trawl of 40 feet head rope, whereas a trawler 
of its size could employ one of 120 feet with resulting 
catch at least six times as great. Notwithstanding 
these drawbacks excellent work was done, 543 
stations having been investigated, generally by 
t-hour trawls, distance traversed 4 miles. While 
the hauls are thus closely comparable, they are 
difficult to collate with commercial fishing. They 
2 Union of South Africa: Fisheries and Marine Biological Survey. Reports 
Nos. 1 and 2 for the years 1920 and 1921. By Dr.J. D. F. Gilchrist. 
NO. 2782, VOL. 111] 

deal entirely with unexplored grounds; we should 
have liked a few on the known grounds, already 
frequented by steam trawlers, for comparison. 
Commercial trawling is now carried on down to 
300 fathoms, and the total area within these depths 
off South Africa is about 120,000 square miles. The 
grounds may be divided into three areas—the eastern 
off the shores from Kosi River to Port Elizabeth, 
625 miles; the southern from the latter to the Cape, 
360 miles; and the western from the Cape to Cunina 
River, 1080 miles. The eastern is mostly a 1o-mile 
belt, sloping off steeply from 60 fathoms; this is 
the region of the Agulhas Current, which causes in 
most places a roughness unsuited to trawling. The 
southern is that of the Agulhas Bank, a name given 
to the southern broad point of the continental slopes, 
its edge 150 miles from the shore. The western 
has a broad slope, not bounded by any marked steep, 
about 60 miles across, half within the roo-fathom 
line; it is on the whole smooth and regular ground, 
and lying on the colder side of the Cape—average 
difference 10° F.—should prove good trawling ground 
with fish of similar quality to those of our own shores. 
The two most important deeper water fish proved 
| to be the stockfish, or Cape hake, and Macrurus, 
But some of them have no suspensor : | 
It is sug- — 
But in fact they are attached laterally, — 

ee 
