— 173 — 



There are several other spore-Hke growths on the strawberry 

 which some writers beheve to be yet other forms of Sphaerella Fra- 

 garicz, but which our experiments thus far have either not dealt with 

 or else given no proof of such connection. These are the "stylo- 

 spores" and the "spermatia" of Tulasne.* Besides the above 

 there are ten or more species of fungi, all presumably distinct from 

 Sphaerella, found parasitic on the Strawberry, none of which, ex- 

 cepting Ascochyta Fragariiz, Sacc, are known to produce any 

 serious disease of the host. 



When a "spot" first appears on a young leaf in June it is 

 brownish, or more usually red or red-purple, and rapidly assumes 

 the character it has at maturity. When fully developed it has a 

 center nearly circular, dead-white, and usually from 3-6 millime- 

 ters {yi-yi of an inch) in diameter. This white center is sur- 

 rounded b/ a distinctly red or purple border 1-3 millimeters wide, 

 which shades into dark purple-brown next to the white center 

 (Fig. i). These spots often join, when the leaf is badly diseased, 

 so as to form a single large discolored area. 



THE MYCELIUM OR VEGETATIVE PORTION. 



The discoloration^ 

 above mentioned are 

 caused by the mycelial 

 stage of the fungus, 

 which, with the sum- 

 mer conidia immedi- 

 ately connected with i.ij,,^ 

 it, are the chief sources 

 of injury to the host- 

 plant. The mycelium 

 ( Fig. 2 ) consists of 

 slender, branched, col- 

 orless filaments, the 

 parts of which, whether for vegetative purposes or not, are often 

 called the hyphce. These filaments are narrower than the conid- 

 ial spores which they bear, varying from .001-.003 of a millimeter 

 in breadth. They push their way between the cells of the interior 

 of the leaf, by contact disorganize the contents of such cells, and 

 absorb their fluids. During this process a red fluid appears in the 



Fig. 2. — Transection of a strawberry- leaf in autumn, show- 

 ing a healtliy portion on the left, and on the right the 

 margin of a " spot." The tissue of the leaf is exhausted 

 by the mj-celium and shrivelled to one-fifth the original 

 thickness, (u. ep.) the upper epidermis ; (1. ep.) the 

 lower epidermis; (c.) cells with chlorophyll; (a.) air 

 spaces of leaf ; (b.) basidia of the fallen conidia. 



*vSee "vSelecta Fuiigoriim Carpologia," II, p. 2SS, PI. XXXI f. 1-9 ; and 

 Ann. d. Sci. Nat., Series IV, Vol. 5, p. 112. 



