Jan. 15,1885] 



NA TUKJi 



-47 



cultural Society in richly-manured kind, and the produce 

 proved abundant, yielding, the first year, 600 tubers as 

 large as pigeons' eggs. The constitutional effects of the ab 

 normal production of tubers which high farming occasions 

 have been often noticed. On this point Mr. Baker says : 

 " Any plant brought to the tuber-bearing state is in a dis- 

 organised, unhealthy condition, a fitting subject for the 

 attacks of fungus and aphides." 



It frequently happens, moreover, that the cultivated 

 potato loses its power of producing flower and of repro- 

 ducing itself In means of seed. The illustrious horticul- 

 turist, Thomas Andrew Knight, discovered the relationship 

 of tuber to fruit, and demonstrated with great clearness 

 the principle that, in proportion as plant; or animals waste 

 in one direction, they must economise in another. Know- 

 ing the difficulties that lay in the path, Lord Cathcart 

 intrusted some tubers of 5. Maglia from the coast of 

 Chili to those eminent potato-breeders, whose collection 

 of varieties Mr. Hiker refers to as the largest in the 

 world, Messrs. Sutton and Sons of Reading. After very- 

 careful treatment of the tubers, which were about the size 

 of walnuts, the young plants were committed to the open 

 ground, where, making our story as short as possible, 

 they grew vigorously and produced numerous blossoms 

 having while corollas, which are characteristic of wild 

 potatoes, the corollas of cultivated breeds being purple 

 and lilac. But whatever the seed-bearing capabilities of 

 iVi may be at Valparaiso and in the Chonos 

 Archipelago, when growing in a state of nature, it did not 

 produce a single seed in Messrs. Suttons' trial-grounds, 

 except in the case of some blossoms which were hybri- 

 dised. It is needless to describe the particular means by 

 which this delicate operation was effected. It happens, 

 however, that the manipulator was the same- veteran 

 breeder who had grown despondent about potatoes until 

 this new- departure had been achieved. Last winter he 

 had reached the end of his tether. Since then he has 

 hybridised Solatium Maglia, and is anticipating the 

 conquest of new potato worlds in his old age. 



The crop at Reading this first year is good, and the 

 tubers are as large as those of ordinary potatoes. The 

 foliage is luxuriant, growing as high as a common table. 

 Certain other so I have shown no capacity for "im- 

 provement." S. 'Jamesii, for example, grows at Reading 

 only eight or ten inches high, and would scarcely be 

 recognised as a potato except by a botanist. 5". Com- 

 7/iersoni, known bv the synonym Ohrondi, from the 

 name of a French naval surgeon who brought it to 

 Brest from Goritti Island, at the mouth of the Rio de 

 la Plata, was obtained last spring by Messrs. Sutton from 

 M. Blanchard of the Gardens of the N ival Hospital at 

 Brest. Messrs Sutton have wisely acted throughout 

 these trials under scientific advice, and \. Commersoni 

 had been named by Mr. Baker as one of the few species 

 which are known at present to have shown a capability 

 of '"improvement.'' Unfortunately it resisted all the 

 attempts that were made last summer tit Reiding to 

 hybridise it with the cultivated sorts. We may hope, 

 however, to become possessed of this and other hybrids 

 before breeders have travelled far on the road which has 

 now been opened to them. Previous attempts to over- 

 come the potato disease had been mainly directed to the 

 doctoring of the soil, or plant, and to direct attacks upon 

 the disea ! rardener and farmer may now wel- 



come the birth, so to speak, of a hybrid, which, we may 

 hope, will enable the potato plant to resist the attack cf 

 parasites, and especially those of the devastating fungus 

 Peronospora infestans. H. E. 



OX THE EVOLUTION OF THE BLOOD- 

 VESSELS OF THE TEST IX THE TUNIC AT A 

 T T is well known that the test or outer tunic in most 

 *■ Simple Ascidians is penetrated by a system of tubes 

 containing blood. These "vessels" were shown in 1-I72 



by Oskar Hertwig x to b 



ations containing prolongations from one of the blood- 

 sinuses of the underlying mantle. Each vessel is divided 

 longitudinally into two distinct tubes by a septum of con- 

 nective tissue, and after ramifying through the test may 

 be found to terminate, generally close to the outer surface, 

 in one or more rounded enlargements or bulbs which are 

 usually known as the "terminal knobs" (Fig. 5, b). The two 

 blood-tubes join in the terminal knob where the septum 

 ends, and this allows the blood which flows n 1 I 

 !| "- one tube ' bul I flnv ! 



Fio. i. — Clavelit. <rmU ■ from a specimen di 



Dartmouth, br , branchial aperture ; itt., atrial aperture ; />r.s , branchial 

 sac ; t.. test ; lit , mintle ; <r , oesophagus ; St.. stomach ; / , intestine ", 

 r., rectum ; en., endostyle ; u.« . nerve ganglion; s. t stolon ; B, part of 

 the stolon becoming enlarged to form a bud. 



along the other tube. Thus temporarily the one tube acts 

 as an artery and the other as a vein, but of course they 

 exchange functions at each reversal of the heart's action. 



This system is usually regarded as being merely the 

 blood-supply to the test ; but Lacaze-Duthiers 2 has 

 pointed out that the hair-like projections from the test to 

 which sand-grains adhere in most Molgulidas, are merely 

 special developments of the terminations of the vessels, 

 and I have suggested 3 that they are also homologous 

 with the vessels in the stolon of the Clavelinidae from 

 which buds are produced (Fig. 1). 



The extent to which this blood-system of the test is 

 developed varies greatly in the different species of Simple 

 Ascidians. In some, such as Ascidia plebeia and Corel/a 

 parallelogramma (Fig. 4), it is very rudimentary, if indeed 

 it can be said to be present ; while in others, such as 

 Ascidia mentula, Ascidia meridionalis, and Ascidia 



1 " Untersuchungen fiber den Bau und die Entwickelung des Cellulose- 

 Mantels der Tunicaten." /,■■ .■ -Id vii.p.46. 



2 Arrhivcs de Zoologie exfierimentaleet gintrale, t m. p. 314, 1874 ; and 

 Com iles Rexdus, t. Ixx.x. p. 600, 1875. 



I /'/ I Roy. Soc. Eain. 1879-80, p. 719. 



