DUBLIN NATUBAL HISTOEY SOCIETY. 29 



by, however, there appears, towards the middle of the frond, one or many- 

 darker longitudinal regions, which soon become bands, subsequently 

 changing to be diaphanous, when the ''utricles" become larger and 

 spherical, sometimes disposed in a single series, sometimes in several, and 

 these, he says, are nourished and increased in size at the expense of the 

 surrounding smaller granules. These larger "vesicles" he now deno- 

 minates " propagules," and states they ultimately make their escape 

 from the parent frond by its dehiscence at the central suture, or are pro- 

 truded, along with the remainder of the endochrome, en masse through a 

 pair of apertures on the under side of the frond. But farther — he be- 

 lieves that the active granules found at the extremities of this plant (as 

 weU, indeed, in all the species of Closterium, and in some species of a few 

 other genera), preparatory to the emission of liis "propagules," leave 

 their position at the extremity of the frond, and, becoming mixed with 

 them, exert a fertilizing function on the latter. The subsequent deve- 

 lopment of these "propagules," he states to consist in theii" gradual 

 elongation from their original spherical form ; the endochrome, with the 

 gradual increase in size of the now young growing frond, becoming se- 

 parated into two portions, the terminal spaces with the active granules 

 soon making their appearance as in the adult Closterium, and further 

 increase in dimensions following, until the full size of the species is 

 attained. He, moreover, describes the act of conjugation (since accu- 

 rately described by Smith, I. c.) ; but, strange to say, he (M. Morren) does 

 not seem to look upon this as a true generative act, so far as I can judge ; 

 but seems to think the sporangium (" seminule") resulting from the act 

 of conjugation is itself fertilized during the process by the agency of the 

 at first terminal motile particles. He states the further development of 

 the spherical sporangium (itself as great in diameter as the old frond), 

 previously undergoing a revolving motion for a few moments, to consist 

 merely in its gradual elongation in two opposite directions, but unequally, 

 thus forming two unequal cones. It is to be supposed, however, that he 

 must imagine the smaller cone would eventually keep up with the longer, 

 so as to restore the synunetry. Such is, briefly, Morren' s account of the 

 reproduction in this plant. 



Professor Smith (I. c. ) gives a nearly similar account of the process 

 of conjugation. The conjugative act in this species is not undertaken till 

 after the two original fronds about to conjugate have undergone self-di- 

 vision in the manner usual in this genus — that is to say, by self-fission, 

 effected by a division of the contents into two just under the suture, 

 accompanied by a development of new cell- wall to each old segment, and 

 separation taking place. The separated portions have now one long (and 

 old) cone, and one more blunt and rounded (the nascent younger one). 

 Now, in those individuals about to conjugate, from each of the shorter 

 or younger cones is protruded a blunt, pouch-like projection from the 

 lower and opposed sides of each, which approaching by gradual growth, 

 the contents from each emerge thereby, and, meeting half way, amalga- 

 mate with each other ; at the same time the other opposite portions of the 

 original parent fronds doing in precisely the same manner. Thus two 



