Desmids from Massachusetts, U.S.A. By Wm. West. 19 



If it be this species it will be new to the United States. 

 Fig. 6. 



C. Broomei Thwaites. Abundant. 



G. speciosum Lund. 



Xantliidium Tylerianum nov. sp. Semi-cells oblong-trapezoid, 

 sometimes oblong-subquadrate, with two pairs of slightly 

 curved short spines on each side of the semi-cell, projecting 

 from widened bases at right angles to the longest axis of the 

 frond, ends elliptic or subelliptic with the spines projecting 

 at the sides. Side view of semi-cells subrotund, no spines 

 showing in the periphery, central protuberances obscure. 

 Empty cells show that the protuberances are very faintly 

 beaded with about eleven granules. Cytoderm faintly 

 punctulate or sometimes smooth. Length-70 /a. Breadth 

 of broadest part without spines, 65-60 fx. Breadth of 

 narrowest part without spines, 42-52 /i. Breadth of 

 broadest part with spines, 70-80 /t. Breadth of isthmus, 

 20-25 yLt. Fig. 1 front view. Fig. 2 side view. Fig. 3 

 end and other views. Figs. 4 and 14 dividing fronds. 



Associated with this were some zygospores; but none of them 

 were attached to the semi-cells of any species. I append figures of 

 four examples of the one mostly seen, fig. 5. Another solitary 

 example was noticed, different from the others, but still not attached 

 to empty semi-cells. Fig. 13. 



The Xanthidium was certainly the most abundant species present, 

 and there were plenty of empty semi-cells. The next species in point 

 of quantity present was Micrasterias truncata Kalfs, Staurastrum 

 S]pongiosum Breb. being next ; a few empty semi-cells of the last two 

 species were seen. Other species sparingly present in the same 

 gathering were Euastrum verrucosum Lund, Cosmarium Cordanum 

 Breb., Cosmarium tripUcatum Wolle, Cosmarium Iseve Kaben., and 

 Staurastrum Sehaldi Eeinsch. 



Arthrodesmus convergens (Ehren.) Ealfs. 



Euastrum oUongum (Grev.) Ealfs. All specimens seen were 

 of different form from British examples. 



E. verrucosum Lund. Abundant. 



E. verrucosum Lund., var. dlatum Wolle. Intermediates 

 between this variety and the type were also noticed. 



E. hinale Ealfs, forma minor* I have noticed this form before 

 in gatherings from Maine, most examples being about 9 /i 

 in breadth, and 11 /i in length ; in this gathering additional 

 examples up to 12 /a in breadth were noticed. Three 

 examples are shown in fig. 24. 



E. crassicoUe Lund. 



E. elegayis Kiitz. 



* V^e Journ. Bot , Nov. 1888, " The Desmids of Maine." 



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