426 PROF. OLIVER ON THE STRUCTURE OF THE ANTHER. 



tive respectively to the petiole or the filament. A consideration of the transitional organs 

 between petals and stamens normally occurring in some plants, as well as in double or 

 abnormal flowers, as, e. g., in the subject of the present paper, compels me to regard the 

 anther as a metamorphosed lamina ; while, further, the pollen is undoubtedly an altered 

 condition of the internal cellular tissue of the leaf, not an external production. I am 

 ignorant of the true nature of these remarkable petiolar " glands," which deserve complete 

 examination. A comparison of some of the above Euphorbiaceous plants suggests the 

 possibility that they indicate, in their case, rudimentary lateral veins, and a tendency in 

 the leaf to become peltate. The opinion that the anther-cells are a formation distinct 

 from lamina or petiole was also held by Link*. After referring to the views of Cassini 

 and Bischoff, he says, " Equidem hasce explicationes nimis hypotheticas et fere mecha- 

 nicas dixerim. Ubi petalum e stamine oritur, lamina petaloidea e filamento excrescit, 

 connecticulum dilatatur et extenuatur, anthera vero ad latus removetur, ubi diminuitur, 

 donee pereat. Nova igitur est formatio antherse, loco folii aut potius loco laminae folii 

 enatse, quae cum folii structura interna vix aliquid commune habet." 



As confirmatory of tlie theory of Bischoff, that the sutural lines of the anther do not 

 coincide morphologically with the margin of the leaf, I consider the evidence afforded by 

 the abnormal stamens of this Geranium. The accompanying outline sketches show 

 transitional forms, from a petaloid lamina slightly thickened at its upper edges only 

 (through a series bearing, besides marginal thickenings, a pair of oblong, more or less 

 thickened masses of parenchyma at each side of the midvein of the leaf, and considerably 

 within its edge), to tolerably perfect stamens with longitudinally lobed anther-cells. 

 And, further, examination of these intermediate forms, I think, clearly shows thcd the 

 sutures of the anther answer to the lines of junction of the outer and inner thickened 

 portions of the lamina on either side of the midrib, and that the septa of " untransformed 

 tissue" may be regarded morphologically as resulting, in part at least, from the inflected 

 epiderms of the adjacent anther-cells. A transverse section of one of the thickened and 

 distinct masses of these abnormal anthers exhibits no median plate of tissue dividing the 

 pollen-parenchyma into anterior and posterior portions, as might, on Cassini and Roeper's 

 view of anther-structure, have been expected. Although it is true that in foliage-leaves 

 it is usual to find the cells of parenchyma towards the upper surface closely packed and 

 often elongated perpendicularly to it, while those of the lower layers are irregular in form 

 and traversed by intercellular passages, yet there can hardly be said to be a clear diffe- 

 rentiation of two layers of tissue, or of an intermediate third layer separating these, to 

 which the septum extending from the connective to the longitudinal furrows on each 

 side of the anther might homologically be referred. On the view which the examination of 

 these imperfect stamens would tend to lead us to adopt of anther- structure, I conceive that 

 many of the less usual forms are more readily explicable than on that commonly received. 

 The anthers of Lauracese, for example, often present the simple condition normally of 

 four lobes — two superior, two inferior — approaching some of the forms figured from the 

 Geranium. As in this order the thickened pollen-cells are not laterally approximated, 

 there is no collateral junction or " suture " which may offer a line of dehiscence, as in the 



* Elementa Phil. Bot. 1837, ii. p. 185. 



