soil, careless cultivation, or a degenerated stock of seed.  Those who save their own seed continuously for years are almost certain to become well acquainted with this malady.  They will find a change of seed necessary, and at the same time an alteration in the routine of culture.  A healthy, vigorous plant, derived from a pure seed-stock, does not easily make Finger-and-toe, but a sound root that stands for food and money.

’Grub.’—­The wart-like growths formed upon the roots of Turnip and Cabbage by the little hard beetle known as the Turnip-gall Weevil, =Ceutorhynchus pleurostigma=, are also quite distinct from Finger-and-toe.  By cutting across a malformed root of Turnip or Cabbage it is usually not difficult to determine the cause of the mischief.  If it is Finger-and-toe the root will be found filled with decaying matter; in the case of Weevil attack the small legless maggots, commonly called ‘Grub,’ will be brought into view; and if it is merely an instance of reversion the cut root will appear to be healthy.

==Potato Disease==.—­The fungus which causes the Potato Disease, or ‘Blight’ as it is sometimes called, was formerly known as =Peronospora infestans=; now it is recognised by scientific authorities as =Phytophthora infestans=.  The mark of its pestilent touch on the foliage, and its destructive effect on the tubers, are unfortunately too familiar in gardens and on farms.  In dry seasons its energies are restricted, but the scourge is never absent, and during wet summers the parasite may do its deadly work on such a vast scale as to cause a Potato famine.  Moisture is a necessity of its existence, and in rotting haulm, decayed tubers, and damp soil the spores remain in a resting condition until they are afforded an opportunity of multiplying with the marvellous rapidity that invests the disease with its terrible power.  A series of six illustrations, five of which are highly magnified, will enable the reader to follow the development of =Phytophthora infestans=.[1]

[Illustration:  No. 1]

The illustration No. 1 shows a Potato leaf on a reduced scale disfigured by the attack of the fungus.  The =Phytophthora= is sending mycelial threads (called hyphae) in all directions through the substance of the leaf, feeding on the protoplasm of the cells and destroying the chlorophyll, or leaf-green, in those cells.

[Illustration:  No. 2]

[Illustration:  No. 3]

No. 2 shows the fungal threads at work.  In a diseased Potato plant these threads, or mycelial hyphae, make their way through the substance of the leaves, and down the haulm into the tubers, from which they consume the food stored there.

No. 3 exhibits the various stages of germination of one of the conidia of =Phytophthora infestans=:  (=a=) the ripe conidium in water; (=b=) protoplasmic contents breaking up into blocks, which separate and escape (=c= and =d=) as minute kidney-shaped zoospores (=e=) each with two cilia; (=f= and =g=) the zoospore coming to rest and losing its cilia; (=h=, =i=, =j=, and =k=) successive stages of germination of the zoospore.