Mr. J. Ralfs on the British Desmidiese. 377 



genera also increase by a new growth interposed in the centre of 

 the frustule. May not the growth in some of the higher Algae 

 also be confined to the centre of the joints, instead of being an 

 extension of parts already formed ? Should this suggestion prove 

 correct, such a fact would be an additional proof of the vegetable 

 nature of the Desmidiea, and may perhaps also lead to further 

 knowledge of the physiology of the Confervece. 



It will be more difficult to ascertain whether this is the case in 

 the latter ; in Tyndaridea however, the genus best adapted for ob- 

 servation, I believe that its occurrence can be proved, for in each 

 joint two stellse are present ; and I think that whilst these always 

 remain distinct on their outer side and at the same distance from 

 the septum, they first become more distant from each other by the 

 growth of the intermediate and central portion of the joint, and 

 that two new stellse are then formed between them, which at first 

 connect the original stellae, and gradually become more distinct 

 as the joint prepares to divide. If this opinion be correct, the 

 new septum will always be formed where the new portion of the 

 joint is formed. At length the plant ceases to grow, the division 

 of the joints is not repeated, the endochrome alters in appearance, 

 the reproductive organs are formed, and the individual perishes. 

 So in the Desmidiece : the fronds at length no longer divide, the 

 internal matter assumes a different appearance, and what I con- 

 sider the reproductive granules are perfected. 



Meyen adduces the presence of starch as a conclusive proof of 

 the vegetable nature of the Desmidiecs. He states that in several 

 genera he has " distinctly seen that the large and small granules 

 contained amylum, and were sometimes even entirely composed 

 of it," and that in the month of May he had observed " many 

 specimens of Closterium in which the whole interior substance was 

 granulated, and all the grains gave with iodine a beautiful blue 

 colour, as is the case with starch, which is not an animal product.'' 

 These experiments if correctly made would appear decisive, but 

 Meyen^s assertions have not been allowed to pass unquestioned. 

 Mr. Dalrymple, in a very able and interesting paper on the Clo- 

 steria^, observes of his own attempts to repeat Meyen's experi- 

 ments, " In no one instance had the action of iodine produced 

 its ordinary eff'ects upon starch or vegetable matter by colouring 

 it violet or blue, although Meyen asserts it did in his trials." In 

 the ' American Journal of Science and Arts,' vol. xli. No. 2, is an 

 article by Professor Bailey, of the U. S. Military Academy, on the 

 American ^^Desmidiacece" in which he gives copious extracts from 

 Mr. Dalrymple's paper accompanied by his own remarks. 

 He bears testimony to the general correctness of Mr. Dalrymple's 



• Annals of Natural History, vol. v. p. 415. 



