228 NEMATOGENJS. 



Nostoc piscinale > "Wittr. & Nord. Alg. Exs. No. 195. 

 Nostoc intricatum, Meneg. Nost. Ital. p. 122. Borzi Alghe 

 Fico. p. 283. 



In ditches (slightly brackish). 



" Forming small roundish gelatinous masses, floating amongst different 

 species of Lemna in fresh water, but probably within the influence of the 

 tide, and also amongst Enteromorpha intestinalis, and even within the 

 frond in brackish water. The plant is at first of an olive yellow gradually 

 assuming a greener tint, and when dried of a deep verdigris. Very 

 gelatinous, delicately branched, the branches very flaccid. Under a high 

 magnifier the whole plant is evidently composed of gelatine, in the centre of 

 which runs a single moniliform filament, following the ramifications, and 

 in its progress curling to and fro repeatedly across the thread, the joints 

 bein_' nearly globular. The specimens from the interior of Enteromorplta 

 are paler, and have longer joints amongst the globular ones." 



Plate LXXXIX. Jig. 1. Nostoc Linkia (intricata) nat. size, after 

 Berkeley. 



Fig. 2. Nostoc completely developed, composed of the interlacings of 

 a single trichome X 350. 



Fig. 3. Portion of trichome, spores arrived at complete maturity X 650. 



Fig. 4. a, spore commencing to germinate ; b, c, d, e, spores in 

 germination more or less advanced X 650. 



Fig. 5. Germinating filament changed into a hormogone X 650. 



Fig. 6. Free hormogone X 650. 



Fig. 7. Motile trichornes segmenting in fragments, of which each 

 constitutes a hormogone. 



Fig. 8. Immovable hormogone commencing to develope X 640. 



Fig. 9. Development of hormogones X 650. 



Fig. 10. Group of spores germinating X 350. 



Fig. 11. Chaplets of spores obtained by cultivation in germination X 

 650. Figs 2 to 11. After Bornet. 



Nostoc piscinale. Kutz. Tab. Phyc. IL, t. 11, /. 3. 



Fronds attached or free swimming, bullate and tuberculate, 

 verdigris green, rarely rnfescent, becoming olivaceous by age. 



Trichomes loosely interwoven, joints equal in diameter, rather 

 distant. Spores subglobose. 



SIZE. Joints 0037-'004 mm., heterocysts '006 mm., spores 

 007 x -008mm. 



Born. & Thuret Notes Alg. ii., 90. 



Nostoc lacustre, Kutz. Tab. Phyc. ii., t. 11, f. 2. Eabh. Alg. 

 Eur. ii., 179. Borzi Alghe Fico. p. 281. 



Nostoc agglutinans, Kutz. Tab. Phyc. ii., t. 10, f. 1. Rabh. 

 Alg. Eur. ii., 178. 



In ditches. 



Plate LXXXIX. jig. 12. Trichomes of N. piscinale X 400 ; fig. 13, 

 portion of trichome with heterocyst x 600 ; fig. 14, spores in course of 

 development, with mature spores X 600; fig. 15, spores in the early 

 stages of germination. X 600. 



