Algals.] 



CONFERVACEyE. 



15 



even asserted by M. Thuret, that in Conferva glomerata and rivularis, the spores have 

 special organs of motion, of the nature of ciliae or tentacnla, and that it is by theu' rapid 

 action tliat the spores swim so freely in fluid. — {Ihid. xix. 267.) Motions of another 

 kind have been noticed in the Oscillatoi'ias ; and in the species called Zygnemas, they 

 are so extraordmary as to approach nearly to the act of eo])ulation in animals. In the 

 language of M. Decaisne, " the spores of these plants result from the couphng of two 



tubes, of which one transmits to the other, by 

 a pecuhar mechanism, the substance which it 

 contained, in order to fonn one or two spores 

 distmct and separated by a partition, wliich is 

 organised after the copulation." In this 

 coming together, the two tubes project one 

 nipple from each of two opposite cells, which 

 by degrees touch, after which, the points of 

 the nipples are absorbed, a passage established 

 between the cells, the colouring matter of one 

 pom-s into the other, till one of the cells is 

 wholly emptied. 



Meyen states, that the red and green 

 Snowplants, which have been described as Confervse, and assigned to the genus 

 Protococcus, are nothing more than the animalcules called Enchelis sanguinea, and 

 Pulvisculus. But this does not affect the genus Protococcus, which contains produc- 

 tions respecting whose vegetable nature no doubt is entertained. 



Hydrodictyon utriculatum has the appearance of a green net. According to M. 

 Areschoug, the cells of this plant, when nearly ripe, contain a number of active spheri- 

 cal granules, which in the process of reproduction become elliptical, and are attached 

 by their exti-emities, when an articulation is soon produced, so as to form pentagons 

 or hexagons. Each gi-anule becomes a cell of the new Hydi'odictyon. {Dr. Hydr. 

 uti'ic. dmertatio.) 



Fig. IV. 



is by this passage that the granules escape. At first they issue in a body, but soon those which remain, 

 swimming in a much larger space, have much more difficulty in escaping, and it is only after innumerable 

 knockings (titubations) against the walls of their prison, that they succeed in finding an exit. From the 

 first instant of the motion one observes that the granules or sporules are furnished with a Httle beak, a 

 kind of anterior process, always distinguishable from the body of the seed by its paler colour. It is on 

 the vibrations of this beak that the motion, as I conceive, depends ; at least, I have never been able to dis- 

 cover any cih^. However, I will not venture to deny the existence of these, for with a very high power of 

 a compound microscope one sees the granules surrounded with a hyaline border, as we find among the 

 ciliated Infusoria on applying a glass of insufficient power. The sporules, during their motion, always 

 present this beak in front of their body, as if it served to show them the way ; but when they cease to 

 move, by bending it back along the side of their body, they resume the spherical form, so that before 

 and after the motion one sees no trace of this beak. The motion of the sporules before their exit from 

 the joint consists principally in quick dartings along the walls of the articulation, knocking themselves 

 against them by innumerable shocks ; and in some cases we are almost forced to believe that it is by this 

 motion of the sporules that the mammilla is foi-med. Escaped from their prison they continue their motion 

 for one or two hours, and retiring always towards the darker edge of the vessel sometimes they prolong 

 their wandering courses, sometimes they remain in the same place, causing their beak to vibrate in rapid 

 circles. Finally, they collect in dense masses, containing innumerable grains, and attach themselves to 

 some extraneous body at the bottom or on the surface of the water, where they hasten to develop fila- 

 ments like those of the mother plant. The spherical sporules elongate at first into egg-shaped bags, 

 attached to the strange body by the narrowest end. Their development only consists in a continual 

 expansion, without emitting any root. The green internal matter divides in the middle by a partition, 

 which appears at first sight as a hyaline mucilage, but which gradually changes into a complete diaphragm. 

 It is thus, by successive divisions of the joint first formed, that the young plant increases. The position 

 of the mammilla in each joint is uncertain, at least I have seen it very diff'erent in neighbouring joints. The 

 exit of the sporules does not take place at the same time in the different joints. One often sees those of 

 one of the articulations already escaped, while in the neighbouring one they are not yet completely formed. 

 Commonly the uppermost joints empty themselves first, so that it is not rare to see all the upper part 

 of a filament entirely transparent, whilst the lower part continues still to develop. In this manner 

 the formation and dissemination of the seeds continue during the whole summer, and thus a single fila- 

 ment suffices for the formation of an infinite quantity of sporules. If one remembers that each joint 

 contains perhaps many hundred of spores, it is not astonishing that the water becomes perfectly covered 

 with them ; so that we might readily take for a Protococcus, or other simple Alga, what areonly the 

 spores of a Confen'a. I suspect that from such a mistake have arisen the theories of metamorphosis 

 proposed by many modem algologists." 



Fig. IV.— Spirogyra quinina (Kutzing). 



