10 Transactions of the Society. 



transverse sections through the apices of two young shoots. In 

 one case phragmospheres and paired nuclei were first seen at about 

 0*20 mm. from the apex. At this level the section, which was 

 irregular in outline owing to the leaf rudiments, was only 0*22 to- 

 0"26 mm. in diameter. In the second case the result obtained 

 was of a similar order, a phragmosphere being observed in the 

 epidermis at 0-24 mm. from the apex. 



The ground tissue of the " head " is, as we have already shown,, 

 characteristically binucleate, but further down the axis we come 

 to a region in which most of the cells are uninucleate. The transi- 

 tion is gradual and cannot be said to occur at any fixed level, but^ 

 in a shoot gathered early in May, 3 to 4 cm. from the apex is a 

 good place to look for it. Phragmospheres have, however, been 

 observed at nearly 6 cm. from the apex, and the binucleate 

 character is very persistent in the case of individual cells, notably 

 certain small, deeply staining elements in the pith which probably 

 contain mucilage. At about 2*5 to 4*5 cm. from the apex, the 

 nuclei, which are mostly single in the cells, begin to become lobed 

 and irregular in outline (PL I, fig. 13) ; further from the apex the 

 lobinsj becomes more marked, and the nuclei become flattened and 

 tend to lie close to the walls. In a shoot about 19 cm. long which 

 was examined, single nuclei, more or less irregular in outline, were 

 found to persist to the base. 



The question of how the transition from two nuclei to one takes 

 place is extremely difficult to answer. As in the case of Eremurus^ 

 there are many bilobed, single nuclei to be found whose appear- 

 ance at first glance suggests that fusion has occurred, and sometimes 

 two nuclei are seen lying in a close proximity which favours this 

 idea. In some plants the number of nucleoli might be a guide to 

 whether fusion had taken place, but in Asparagus no help is to be 

 looked for in this direction, since the number of nucleoli is liable 

 to much variation. Por instance, in the same section four cells 

 were observed, each with a pair of nuclei, containing nucleoli in 

 the following numbers : — 1, and 1 ; 2, and 1 ; 2, and 2 ; 3, and 3. 

 I am inclined to think that fusions, if they ever occur, are of 

 entirely subordinate importance in reducing the number of nuclei, 

 the main reason for this opinion being that the bilobed character^ 

 which is so conspicuous a feature of some of the older nuclei, seems 

 to arise gradually, and at a somewhat later stage than the transi- 

 tion from two nuclei to one. The importance of bilobing is also 

 diminished when we see (as in PI. I, fig. 13) tliat it is not universal, 

 some of the nuclei being lobed quite irregularly. If fusion be 

 excluded, another possibility which must be considered is the 

 deferred production of walls between the paired nuclei ; but of this 

 our observations have furnished no evidence whatever, and the 

 probabilities seem to be altogether against such an occurrence. 

 The phragmoplast, in the case of binucleate cells, was converted 



