GLASS STRUCTURES AND APPLIANCES 



221 



ferment, whicii converts them into a soapy fluid, 

 capable of absorption. 



" Asparag-in," and certain nitrogenous substances 

 of like character, seem to have the property of com- 

 bining with tei-nary compounds, and of thus creating 

 new protoplasm. When the ternary compounds are 

 deficient, the asparagin collects in the cells ; but 

 when the compounds in question reappear, then the 

 asparagin combines with them to constitute new 

 albuminoid or protoplasmic matters. But this, 

 again, is a matter demanding further elucidation by 

 the chemist. 



The Descending Sap. — The substances con- 

 cocted in the leaf in the manner briefly alluded to 

 have to pass from the leaf to the place of storage, to 

 the spot where they are required for immediate use, 

 or fH)m the store-place to the growing points after 

 an interval of greater or less duration. In any 

 case these fluids constitute what used to be called 

 the "descending sap,'' an expression it would be 

 better to abolish, because it is likely to .mislead into 

 the belief that it is a fluid of uniform constitution, 

 travelling in a definite direction. In fact it flows in 

 any direction where there may be a stimulus or a 

 call for it, and where the structure of the plant 

 permits its passage. It must not be supposed that it 

 does not sometimes descend, but it is not limited in 

 the direction it takes ; thus, while it goes down from 

 the leaves to the haulm of the Potato to aid in the 

 formation of the tubers, it must needs go up again 

 to form the new haulm which springs from the 

 tubers. So in the Wheat plant the " elaborated 

 sap " must needs go up from the leaves into the ear. 

 Again, in the pendulous branches of a Weeping Ash, 

 for instance, the so-called " descending sap " must 

 necessarily rise from the leaves. But while the 

 direction of the current is thus variable accoi-ding 

 to circumstances, and often different in different 

 parts of the same plant at the same time, there is 

 a greater degree of fixity as to the particular places 

 and tissues in which it may be found ; thus, in an 

 ordinary tree, while the ascending current of water 

 flows, or is forced upwards, chiefly through the wood- 

 cells of the young wood, the so-called elaborated sap 

 is chiefly to be met with in the innermost layers of 

 bark, and in certain special tissues such as the sieve- 

 tubes, the latex-canals, &c. In most trees the princi- 

 pal growth in diameter is brought about by increased 

 cell-formation on the outer side of the wood and on 

 the inner side of the bark respectively. The posi- 

 tion of the "cambium," descending sap," " or- 

 ganisablo matter," or whatever it be called, is thus 

 seen to be most appropriate. When a bud is inserted 

 as in the operation of " budding," it is placed in 

 the midst of this store of food and building material. 



GLASS STEUCTUEES AND 

 APPLIANCES. 



PITS. 



rpHESE may be described as fixed glass frames 

 X placed on brick or other walls. The idea of 

 being sunk into the earth is also associated with that 

 of pits. But, in fact, there are surface as well as 

 sunken pits, and any permanent wall spanned with a 

 glass top is technically and correctly a pit. It is 

 the fixity of the walls, in fact, rather than that of 

 the roof, that forms the pit ; for hundreds of pits 

 are covered with movable sashes, exactly the same 

 as those on frames. Generally, pits may be said to 

 be fixtures, while frames are portable. 



The chief feature of frames is their portability. 

 Pits, from the nature of their material and character 

 of construction, are more of fixtures. Built in the 

 ordinary way, of brick, stone, cement, or concrete, 

 they are landlord's fixtures; that is, no matter who 

 built or paid for them, so soon as up they become 

 the property of the landlord ; and this even though 

 built of wood, if fixed in position by stakes driven 

 into the ground. All pits, however, may be con- 

 verted into tenant's fixtures by the simple device of 

 building them upon, rather than into, the earth. In 

 these days of the rapid increase of horticultural 

 glass-houses and other appliances, and frequent 

 changes of residence, it is important to bear the dis- 

 tinctions between common and tenant's fixtures in 

 mind. The latter can hardly be said to be fixtures 

 at all. Were the tenant to remove every three 

 months, he could take such pits or glass-houses wdth 

 him, without legal let or hindrance. To constitute 

 any building a tenant's fixture, a plank or baulk of 

 timber or a bar of u'on must interpose between it 

 and the earth. To be built on the surface merely, 

 without being sunk in the ground, is not sufficient. 

 A horizontal barrier of some kind must interpose. 

 This cuts through the legal right of landlords to 

 appropriate as their own the property of tenants 

 placed by the latter on their land. 



Such unpleasant contingencies may, of course, be 

 averted by previous agreement, the landlord agree- 

 ing to take tenant-built structures and appliances at 

 a fair valuation. But agreements are not always 

 practicable nor satisfactory, and in this respect they 

 are less needed than formerly, for most builders now 

 so thoroughly understand the law of tenant's fixtures, 

 and have so moulded their pits, green-houses, con- 

 servatories, summer-houses, &c., that they continue 

 from first to last the property of the tenant. Nor is 

 this all, for not a few of them are so constructed 

 that they may readily be taken to pieces and recon- 

 structed with a minimum amount of labour, risk, 

 and cost. 



