8 M. G. Thuret on the Reproduction of certain Nostochinese. 



licheniforme, Kiitz.). In this species the sporanges are smooth, 

 and of a deep brownish red when they are perfectly ripe. In 

 the spring of the present year (1857), I detached a few frag- 

 ments of these specimens, which I had preserved in the herba- 

 rium for nine years, and subjected them to the same experi- 

 ments as the preceding. A fortnight had scarcely elapsed when 

 a great number of sporanges began to open, and to emit the 

 summit of the young filament. I have repeated this experiment 

 several times with the same success ; and in those which I made 

 this summer, I have often seen the spores germinate at the end 

 of six or seven days. The germination of this species exactly 

 resembles that of the preceding. Only the little portion of the 

 wall of the sporange, lifted up by the spore like an operculum, 

 is not carried away at the summit of the filament, but remains 

 attached laterally upon the sporange (fig. 7). 



I should have desired to have made the same trials with spe- 

 cimens of still greater age. It would be interesting to ascertain 

 how long a time the spores of Anabaina can preserve their 

 faculty of germination. But the success of these experiments 

 requires, as I have said before, that the spores shall be perfectly 

 ripe. Now, it is more rare than one would suppose, to find them 

 in this state in herbaria. I have assured myself of this by ex- 

 amining all the specimens in my collection and that of Bory 

 St. Vincent ; and this difficulty has prevented me from carrying 

 my researches any further. 



EXPLANATION OF PLATE I. 



[All the figures are magnified 330 diameters.] 



Fig. 1. Two of the filaments or chaplets filling the interior of Nostoc vesi- 

 carium, DC. 



Fig. 2. Chaplet clothed by a transparent membrane. 



Fig. 3. Chaplet, of which the globules are enlarged and beginning to 

 divide. 



Fig. 4. Chaplet with the multiplication of the globules more advanced. 



Fig. 5. Course of development of the chaplets into new fronds. 



Fig. 6. Two sporanges of Anabaina (Cylindrospermum) licheniformis, Bory. 

 That on the left contains a spore; the other is empty. The 

 membrane of the latter exhibits slight punctations. 



Fig. 7- Germination of the same. The spore pierces the summit of the 

 sporange, and elongates into a moniliform filament, which soon 

 becomes similar to that of the mother-plant. 



Fig. 8. The filaments of A. (Cylindrospermum) major, Kiitz., in different 

 states. That on the left is the youngest. The terminal joint, 

 rounded at the free extremity, is beginning to change into a 

 heterocyst. In the next the heterocyst is already formed, and 

 surrounded by a few mucous threads. In the third the sporange 

 is beginning to develope. 



Fig. 9. Filament with a sporange formed at each extremity. 



