242 Dr. Schleiden 07i the Development of the 



be independent of the carpellary leaves, during its growth, 

 most strikingly in the Ahietinece. My investigations of the 

 earliest conditions have shown me that the organ which, 

 since the researches of R. Brown, has been considered as an 

 open ovarium, is only a scale-like expanded placenta, and that 

 the organ which R. Brown has named bractea is the actual 

 carpellary leaf (fig. 18). This result has been confirmed to 

 me in a most beautiful manner by a cone of Firms alba^ 

 found this spring, which upon the upper half was covered 

 with female and upon the lower with male flowers. In the 

 Ahietinece the placenta, left without the least constraint, de- 

 velops itself to such an extent, that at length the carpellary 

 leaf itself appears as a mere supplementary part. The more 

 extended detail of these investigations being here out of place, 

 I must beg to refer to a work on which I am at present en- 

 gaged, upon which I have been occupied some years with 

 great interest, and which is intended to include the perfect 

 history of vegetable development in every department. 



In all this variety of forms of the ovulum-bearing axis, whe- 

 ther it grows upwards upon the carpellary leaves or elevates 

 itself free in the middle, there frequently occurs the additional 

 peculiarity, that besides the reflexion sustained by the axis, 

 which has been so often alluded to, there is another to which 

 it is subject in consequence of the space being too limited su- 

 periorly for the development of the ovular-bud ; the ovulum 

 hmizontale and pendulum, with their various intermediate 

 states, are hereby formed. This modification, however, 

 proceeding, as it appears to do, merely from an external ne- 

 cessity, viz., the extent of space allotted to it, is of far less 

 consequence than the first-mentioned reflexion ; and we find 

 accordingly in one and the same family (in the Dtyadecc, for 

 instance) both pendent and erect ovules, but it seldom occurs 

 in a highly developed family, and probably only in the Aroidece, 

 that atropous and anatropous ovules are found together. For 

 this reason the definition of a radicida supera or infera in bo- 

 tanical descriptions possesses little or no value, when regard 

 has not at the same time been had to the internal formation 

 of the ovule. 



As we found that there was a peculiar development of the 

 cellular tissue in the anthers, by means of which the leaf be- 

 comes converted into an organ for the production of pollen, so 

 we observe also that there is a peculiar modification of cellular 

 tissue in the summit of the axis or nucleus, by which it likewise 

 becomes adapted to the taking on of a new organism. One of 

 the parenchymatous cells, namely, develops itself to a much 

 gi'eater extent than the others, indeed out of all proportion, 



