. fully developed and of average size 
490 DR. OTTO STAPF ON THE 
slender (Pl. 45. fig. 4, 7/.). It measures not more than 0'4—0*5 mm.? in cross-section, of 
which more than one half goes to the dry parenchymatic cortex, whilst the stereome and 
mestome of the central cylinder are approximately in the proportion of 3: 1 (Pl. 47. 
fig. 57) *. It is true a portion of the products of assimilation deposited in the fruit has, 
no doubt, originated in the chlorophyll of the collenchyma of the pericarp ; but it is not 
probable that this relieves the strain on the mother-plant as the main source of supply 
to any considerable extent, and the water in any case has to come entirely through the 
narrow channels of the stalk. The complete cuticularization and the thickening 
of the epidermis as well as its silicification must thus be a great aid for the plant 
in economizing the water-supply -by reducing the transpiration to a minimum, at 
the same time contributing to the efficiency of the epidermis as a mechanical tissue. 
Mechanical is also the function of the collenchyma in so far as it provides for the 
necessary rigidity of the growing fruit, and in the mature state adds to the strength 
of the pericarp, resulting from the thick cell-walls of its parenchyma. ‘Thus the 
deposition of a portion of the reserves as cellulose has incidentally a considerable 
mechanical effect in the direction of compressive strength, which is very important 
considering the height from which the fruits fall. Otherwise, however, there is little in 
the pericarp to protect it and the enclosed seed for any length of time from the attacks 
of the animal and vegetable world and destructive atmospheric influences. The 
Melocanna fruit is evidently not built for a lengthy period of rest. To speak of the 
seed, we have seen that it is naked. In fact, the term “seed,” in the usual sense, is 
scarcely applicable to it. There is, ab initio, no integument to forma testa, and the free 
ovule-wall corresponds to so small a fraction of the full-grown embryo-sac, and is lost so 
completely in the pericarp, that any function the testa has in the ordinary grass-seed, be 
it in the nascent or the final state, must devolve on the pericarp. So far as they are 
purely mechanical they are, in the presence of the powerful pericarp and the absence of 
a resting period, certainly a negligible quantity. On the other hand, if the nascent 
testa of the typical caryopsis, that is the inner integument of the maturi ing seed, acts as 
passage or transfusion tissue in the sense of "'sehirch's * Náhrschicht' T, this function is 
taken over by the innermost layers of the periearp, which supply immediately the 
maturing seed with water and nutrient matter. The typical store-organ of the fruit of 
the Graminez is the endosperm. In Melocanna endosperm is formed, but its formation 
does “not go much beyond the initial stages. It is soon exhausted, collapses, and is 
finally crushed into an apparently structureless film, wedged in between pericarp and 
scutellum. To compensate the loss of the endosperm, the storage of nutrient matter is 
shifted on partly to the pericarp, partly to the scutellum, and cellulose has been added in 
the former to the usual reserve materials of the grass-seed. Curiously enough, the normal 
* The dimensions measured in a typical case were :—cross-section » Just below the flowering ant O44 mm.” ; 
cortex 0-232 mm.*; central cylinder 0-206 mm.’; stereome 0-149 mm? ; mestome 0:0574 mm" The fruit was 
T See Tschirch, * Angewandte Pflanzenanatomie, p. 459; and Holfert, * Nührschicht der Samenschalen," in 
* = 1890, pp. 279-313, 
